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	$113.50	8.819%	$123.5096	$123.51	$123.50	$123.50
Purchase #2	$122.50	11.261%	$136.2947	$136.29	$136.30	$136.30
Purchase #3	$192.84	7.592%	$207.4804	$207.48	$207.50	$207.50
Purchase #4	$104.96	10.301%	$115.7719	$115.77	$115.75	$115.80
Purchase #5	$224.60	8.562%	$243.8303	$243.83	$243.85	$243.80
Purchase #6	$53.66	10.419%	$59.2508	$59.25	$59.25	$59.30
Purchase #7	$125.40	11.142%	$139.3721	$139.37	$139.35	$139.40
7 purchase totals =	$937.46		$1,025.5098	$1,025.50	$1,025.50	$1,025.60