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	$186.67	4.512%	$195.0926	$195.09	$195.10	$195.10
Purchase #2	$209.57	6.588%	$223.3765	$223.38	$223.40	$223.40
Purchase #3	$235.86	3.653%	$244.476	$244.48	$244.50	$244.50
Purchase #4	$219.41	9.195%	$239.5847	$239.58	$239.60	$239.60
Purchase #5	$228.74	11.659%	$255.4088	$255.41	$255.40	$255.40
Purchase #6	$55.78	6.500%	$59.4057	$59.41	$59.40	$59.40
Purchase #7	$246.76	11.411%	$274.9178	$274.92	$274.90	$274.90
7 purchase totals =	$1,382.79		$1,492.2621	$1,492.27	$1,492.30	$1,492.30