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	$85.51	12.765%	$96.4254	$96.43	$96.45	$96.40
Purchase #2	$11.63	4.484%	$12.1515	$12.15	$12.15	$12.20
Purchase #3	$32.64	10.476%	$36.0594	$36.06	$36.05	$36.10
Purchase #4	$58.69	12.330%	$65.9265	$65.93	$65.95	$65.90
Purchase #5	$61.50	8.423%	$66.6801	$66.68	$66.70	$66.70
Purchase #6	$127.41	3.482%	$131.8464	$131.85	$131.85	$131.80
Purchase #7	$86.75	13.134%	$98.1437	$98.14	$98.15	$98.10
7 purchase totals =	$464.13		$507.2330	$507.24	$507.30	$507.20