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	$146.52	3.228%	$151.2497	$151.25	$151.25	$151.20
Purchase #2	$150.99	7.243%	$161.9262	$161.93	$161.95	$161.90
Purchase #3	$104.37	11.571%	$116.4467	$116.45	$116.45	$116.40
Purchase #4	$168.42	6.629%	$179.5846	$179.58	$179.60	$179.60
Purchase #5	$225.74	11.562%	$251.8401	$251.84	$251.85	$251.80
Purchase #6	$37.33	9.587%	$40.9088	$40.91	$40.90	$40.90
Purchase #7	$37.94	4.679%	$39.7152	$39.72	$39.70	$39.70
7 purchase totals =	$871.31		$941.6713	$941.68	$941.70	$941.50