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	$125.64	4.839%	$131.7197	$131.72	$131.70	$131.70
Purchase #2	$208.76	12.714%	$235.3017	$235.30	$235.30	$235.30
Purchase #3	$71.53	11.449%	$79.7195	$79.72	$79.70	$79.70
Purchase #4	$14.35	3.766%	$14.8904	$14.89	$14.90	$14.90
Purchase #5	$172.74	5.860%	$182.8626	$182.86	$182.85	$182.90
Purchase #6	$223.77	8.735%	$243.3163	$243.32	$243.30	$243.30
Purchase #7	$172.58	10.754%	$191.1393	$191.14	$191.15	$191.10
7 purchase totals =	$989.37		$1,078.9495	$1,078.95	$1,078.90	$1,078.90