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	$186.57	9.549%	$204.3856	$204.39	$204.40	$204.40
Purchase #2	$55.76	7.556%	$59.9732	$59.97	$59.95	$60.00
Purchase #3	$82.76	10.547%	$91.4887	$91.49	$91.50	$91.50
Purchase #4	$196.58	13.585%	$223.2854	$223.29	$223.30	$223.30
Purchase #5	$199.30	4.419%	$208.1071	$208.11	$208.10	$208.10
Purchase #6	$200.59	8.353%	$217.3453	$217.35	$217.35	$217.30
Purchase #7	$165.66	12.203%	$185.8755	$185.88	$185.90	$185.90
7 purchase totals =	$1,087.22		$1,190.4608	$1,190.48	$1,190.50	$1,190.50