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	$241.55	9.586%	$264.705	$264.71	$264.70	$264.70
Purchase #2	$216.52	13.582%	$245.9277	$245.93	$245.95	$245.90
Purchase #3	$217.54	11.855%	$243.3294	$243.33	$243.35	$243.30
Purchase #4	$182.81	7.462%	$196.4513	$196.45	$196.45	$196.50
Purchase #5	$175.32	11.274%	$195.0856	$195.09	$195.10	$195.10
Purchase #6	$158.91	9.455%	$173.9349	$173.93	$173.95	$173.90
Purchase #7	$175.95	5.468%	$185.5709	$185.57	$185.55	$185.60
7 purchase totals =	$1,368.60		$1,505.0048	$1,505.01	$1,505.05	$1,505.00