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	$211.79	9.517%	$231.9461	$231.95	$231.95	$231.90
Purchase #2	$98.82	13.239%	$111.9028	$111.90	$111.90	$111.90
Purchase #3	$172.25	9.869%	$189.2494	$189.25	$189.25	$189.20
Purchase #4	$235.35	12.344%	$264.4016	$264.40	$264.40	$264.40
Purchase #5	$47.61	5.595%	$50.2738	$50.27	$50.25	$50.30
Purchase #6	$46.82	3.752%	$48.5767	$48.58	$48.60	$48.60
Purchase #7	$131.41	10.499%	$145.2067	$145.21	$145.20	$145.20
7 purchase totals =	$944.05		$1,041.5571	$1,041.56	$1,041.55	$1,041.50