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	$72.73	6.690%	$77.5956	$77.60	$77.60	$77.60
Purchase #2	$201.37	3.428%	$208.273	$208.27	$208.25	$208.30
Purchase #3	$129.31	10.810%	$143.2884	$143.29	$143.30	$143.30
Purchase #4	$222.33	3.265%	$229.5891	$229.59	$229.60	$229.60
Purchase #5	$134.98	7.370%	$144.928	$144.93	$144.95	$144.90
Purchase #6	$7.59	13.228%	$8.594	$8.59	$8.60	$8.60
Purchase #7	$195.72	8.505%	$212.366	$212.37	$212.35	$212.40
7 purchase totals =	$964.03		$1,024.6341	$1,024.64	$1,024.65	$1,024.70