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	$91.81	9.494%	$100.5264	$100.53	$100.55	$100.50
Purchase #2	$74.58	6.394%	$79.3486	$79.35	$79.35	$79.30
Purchase #3	$200.55	13.294%	$227.2111	$227.21	$227.20	$227.20
Purchase #4	$48.55	12.275%	$54.5095	$54.51	$54.50	$54.50
Purchase #5	$55.75	9.862%	$61.2481	$61.25	$61.25	$61.20
Purchase #6	$152.73	6.218%	$162.2268	$162.23	$162.25	$162.20
Purchase #7	$184.96	8.473%	$200.6317	$200.63	$200.65	$200.60
7 purchase totals =	$808.93		$885.7022	$885.71	$885.75	$885.50