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	$216.25	13.546%	$245.5432	$245.54	$245.55	$245.50
Purchase #2	$226.61	9.148%	$247.3403	$247.34	$247.35	$247.30
Purchase #3	$245.61	13.328%	$278.3449	$278.34	$278.35	$278.30
Purchase #4	$125.63	4.153%	$130.8474	$130.85	$130.85	$130.80
Purchase #5	$142.33	7.126%	$152.4724	$152.47	$152.45	$152.50
Purchase #6	$131.25	11.449%	$146.2768	$146.28	$146.30	$146.30
Purchase #7	$164.34	12.133%	$184.2794	$184.28	$184.30	$184.30
7 purchase totals =	$1,252.02		$1,385.1044	$1,385.10	$1,385.15	$1,385.00