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	$55.26	7.711%	$59.5211	$59.52	$59.50	$59.50
Purchase #2	$30.54	7.421%	$32.8064	$32.81	$32.80	$32.80
Purchase #3	$21.29	5.512%	$22.4635	$22.46	$22.45	$22.50
Purchase #4	$245.94	7.396%	$264.1297	$264.13	$264.15	$264.10
Purchase #5	$239.70	6.166%	$254.4799	$254.48	$254.50	$254.50
Purchase #6	$160.54	9.423%	$175.6677	$175.67	$175.65	$175.70
Purchase #7	$10.92	4.800%	$11.4442	$11.44	$11.45	$11.40
7 purchase totals =	$764.19		$820.5125	$820.51	$820.50	$820.50