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	$145.40	4.143%	$151.4239	$151.42	$151.40	$151.40
Purchase #2	$221.72	5.288%	$233.4446	$233.44	$233.45	$233.40
Purchase #3	$85.89	13.629%	$97.5959	$97.60	$97.60	$97.60
Purchase #4	$189.51	4.244%	$197.5528	$197.55	$197.55	$197.60
Purchase #5	$136.60	9.337%	$149.3543	$149.35	$149.35	$149.40
Purchase #6	$59.31	3.455%	$61.3592	$61.36	$61.35	$61.40
Purchase #7	$39.29	3.621%	$40.7127	$40.71	$40.70	$40.70
7 purchase totals =	$877.72		$931.4434	$931.43	$931.40	$931.50