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	$197.83	9.526%	$216.6753	$216.68	$216.70	$216.70
Purchase #2	$61.32	13.871%	$69.8257	$69.83	$69.85	$69.80
Purchase #3	$67.39	3.851%	$69.9852	$69.99	$70.00	$70.00
Purchase #4	$93.93	11.785%	$104.9997	$105.00	$105.00	$105.00
Purchase #5	$141.65	8.337%	$153.4594	$153.46	$153.45	$153.50
Purchase #6	$37.84	5.655%	$39.9799	$39.98	$40.00	$40.00
Purchase #7	$11.86	5.229%	$12.4802	$12.48	$12.50	$12.50
7 purchase totals =	$611.82		$667.4054	$667.42	$667.50	$667.50