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	$233.51	10.557%	$258.1617	$258.16	$258.15	$258.20
Purchase #2	$151.97	8.646%	$165.1093	$165.11	$165.10	$165.10
Purchase #3	$136.50	11.255%	$151.8631	$151.86	$151.85	$151.90
Purchase #4	$113.44	9.157%	$123.8277	$123.83	$123.85	$123.80
Purchase #5	$159.36	10.114%	$175.4777	$175.48	$175.50	$175.50
Purchase #6	$100.77	12.106%	$112.9692	$112.97	$112.95	$113.00
Purchase #7	$185.39	11.586%	$206.8693	$206.87	$206.85	$206.90
7 purchase totals =	$1,080.94		$1,194.2780	$1,194.28	$1,194.25	$1,194.40