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	$86.47	3.112%	$89.1609	$89.16	$89.15	$89.20
Purchase #2	$154.90	13.306%	$175.511	$175.51	$175.50	$175.50
Purchase #3	$71.78	6.501%	$76.4464	$76.45	$76.45	$76.40
Purchase #4	$223.30	5.636%	$235.8852	$235.89	$235.90	$235.90
Purchase #5	$34.92	6.228%	$37.0948	$37.09	$37.10	$37.10
Purchase #6	$229.91	7.491%	$247.1326	$247.13	$247.15	$247.10
Purchase #7	$135.53	3.440%	$140.1922	$140.19	$140.20	$140.20
7 purchase totals =	$936.81		$1,001.4231	$1,001.42	$1,001.45	$1,001.40