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	$130.26	10.856%	$144.401	$144.40	$144.40	$144.40
Purchase #2	$233.28	11.417%	$259.9136	$259.91	$259.90	$259.90
Purchase #3	$54.39	8.647%	$59.0931	$59.09	$59.10	$59.10
Purchase #4	$83.75	5.293%	$88.1829	$88.18	$88.20	$88.20
Purchase #5	$79.30	12.221%	$88.9913	$88.99	$89.00	$89.00
Purchase #6	$182.98	6.651%	$195.15	$195.15	$195.15	$195.20
Purchase #7	$165.36	12.253%	$185.6216	$185.62	$185.60	$185.60
7 purchase totals =	$929.32		$1,021.3535	$1,021.34	$1,021.35	$1,021.40