Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$109.97	4.235%	$114.6272	$114.63	$114.65	$114.60
Purchase #2	$59.69	7.194%	$63.9841	$63.98	$64.00	$64.00
Purchase #3	$234.39	3.800%	$243.2968	$243.30	$243.30	$243.30
Purchase #4	$169.75	10.700%	$187.9133	$187.91	$187.90	$187.90
Purchase #5	$40.98	10.179%	$45.1514	$45.15	$45.15	$45.20
Purchase #6	$159.77	7.316%	$171.4588	$171.46	$171.45	$171.50
Purchase #7	$232.46	11.180%	$258.449	$258.45	$258.45	$258.40
7 purchase totals =	$1,007.01		$1,084.8806	$1,084.88	$1,084.90	$1,084.90