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	$221.33	6.261%	$235.1875	$235.19	$235.20	$235.20
Purchase #2	$26.28	6.622%	$28.0203	$28.02	$28.00	$28.00
Purchase #3	$92.89	7.105%	$99.4898	$99.49	$99.50	$99.50
Purchase #4	$57.93	6.485%	$61.6868	$61.69	$61.70	$61.70
Purchase #5	$91.45	9.216%	$99.878	$99.88	$99.90	$99.90
Purchase #6	$152.64	8.604%	$165.7731	$165.77	$165.75	$165.80
Purchase #7	$163.92	11.429%	$182.6544	$182.65	$182.65	$182.70
7 purchase totals =	$806.44		$872.6899	$872.69	$872.70	$872.80