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	$212.73	11.484%	$237.1599	$237.16	$237.15	$237.20
Purchase #2	$235.51	11.323%	$262.1768	$262.18	$262.20	$262.20
Purchase #3	$89.74	6.851%	$95.8881	$95.89	$95.90	$95.90
Purchase #4	$100.81	4.762%	$105.6106	$105.61	$105.60	$105.60
Purchase #5	$32.46	8.776%	$35.3087	$35.31	$35.30	$35.30
Purchase #6	$81.73	9.680%	$89.6415	$89.64	$89.65	$89.60
Purchase #7	$41.96	7.200%	$44.9811	$44.98	$45.00	$45.00
7 purchase totals =	$794.94		$870.7667	$870.77	$870.80	$870.80