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	$162.84	13.317%	$184.5254	$184.53	$184.55	$184.50
Purchase #2	$26.82	5.244%	$28.2264	$28.23	$28.25	$28.20
Purchase #3	$56.59	4.780%	$59.295	$59.30	$59.30	$59.30
Purchase #4	$59.51	4.385%	$62.1195	$62.12	$62.10	$62.10
Purchase #5	$137.45	12.859%	$155.1247	$155.12	$155.10	$155.10
Purchase #6	$247.93	11.686%	$276.9031	$276.90	$276.90	$276.90
Purchase #7	$225.53	10.731%	$249.7316	$249.73	$249.75	$249.70
7 purchase totals =	$916.67		$1,015.9257	$1,015.93	$1,015.95	$1,015.80