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	$232.87	9.677%	$255.4048	$255.40	$255.40	$255.40
Purchase #2	$115.53	9.293%	$126.2662	$126.27	$126.25	$126.30
Purchase #3	$67.62	13.114%	$76.4877	$76.49	$76.50	$76.50
Purchase #4	$118.74	8.588%	$128.9374	$128.94	$128.95	$128.90
Purchase #5	$151.78	13.733%	$172.6239	$172.62	$172.60	$172.60
Purchase #6	$167.64	4.483%	$175.1553	$175.16	$175.15	$175.20
Purchase #7	$192.40	12.433%	$216.3211	$216.32	$216.30	$216.30
7 purchase totals =	$1,046.58		$1,151.1964	$1,151.20	$1,151.15	$1,151.20