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	$69.66	5.120%	$73.2266	$73.23	$73.25	$73.20
Purchase #2	$53.98	7.221%	$57.8779	$57.88	$57.90	$57.90
Purchase #3	$63.87	5.460%	$67.3573	$67.36	$67.35	$67.40
Purchase #4	$74.76	7.499%	$80.3663	$80.37	$80.35	$80.40
Purchase #5	$153.46	7.853%	$165.5112	$165.51	$165.50	$165.50
Purchase #6	$93.98	5.763%	$99.3961	$99.40	$99.40	$99.40
Purchase #7	$223.68	8.643%	$243.0127	$243.01	$243.00	$243.00
7 purchase totals =	$733.39		$786.7481	$786.76	$786.75	$786.80