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	$77.61	13.500%	$88.0874	$88.09	$88.10	$88.10
Purchase #2	$81.96	11.198%	$91.1379	$91.14	$91.15	$91.10
Purchase #3	$161.58	10.297%	$178.2179	$178.22	$178.20	$178.20
Purchase #4	$91.30	10.152%	$100.5688	$100.57	$100.55	$100.60
Purchase #5	$151.68	9.123%	$165.5178	$165.52	$165.50	$165.50
Purchase #6	$194.54	11.331%	$216.5833	$216.58	$216.60	$216.60
Purchase #7	$93.78	12.780%	$105.7651	$105.77	$105.75	$105.80
7 purchase totals =	$852.45		$945.8782	$945.89	$945.85	$945.90