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	$154.33	3.451%	$159.6559	$159.66	$159.65	$159.70
Purchase #2	$67.89	6.871%	$72.5547	$72.55	$72.55	$72.60
Purchase #3	$24.35	10.176%	$26.8279	$26.83	$26.85	$26.80
Purchase #4	$168.90	9.836%	$185.513	$185.51	$185.50	$185.50
Purchase #5	$165.37	7.844%	$178.3416	$178.34	$178.35	$178.30
Purchase #6	$155.92	9.175%	$170.2257	$170.23	$170.25	$170.20
Purchase #7	$206.76	11.160%	$229.8344	$229.83	$229.85	$229.80
7 purchase totals =	$943.52		$1,022.9532	$1,022.95	$1,023.00	$1,022.90