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	$57.35	3.707%	$59.476	$59.48	$59.50	$59.50
Purchase #2	$243.78	8.637%	$264.8353	$264.84	$264.85	$264.80
Purchase #3	$179.59	9.508%	$196.6654	$196.67	$196.65	$196.70
Purchase #4	$128.72	5.300%	$135.5422	$135.54	$135.55	$135.50
Purchase #5	$17.82	10.364%	$19.6669	$19.67	$19.65	$19.70
Purchase #6	$192.42	9.285%	$210.2862	$210.29	$210.30	$210.30
Purchase #7	$203.30	8.140%	$219.8486	$219.85	$219.85	$219.80
7 purchase totals =	$1,022.98		$1,106.3206	$1,106.34	$1,106.35	$1,106.30