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	$133.45	4.649%	$139.6541	$139.65	$139.65	$139.70
Purchase #2	$47.80	5.385%	$50.374	$50.37	$50.35	$50.40
Purchase #3	$147.97	3.176%	$152.6695	$152.67	$152.65	$152.70
Purchase #4	$85.92	5.846%	$90.9429	$90.94	$90.95	$90.90
Purchase #5	$39.65	7.605%	$42.6654	$42.67	$42.65	$42.70
Purchase #6	$210.27	6.391%	$223.7084	$223.71	$223.70	$223.70
Purchase #7	$229.60	11.795%	$256.6813	$256.68	$256.70	$256.70
7 purchase totals =	$894.66		$956.6956	$956.69	$956.65	$956.80