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	$131.51	11.182%	$146.2154	$146.22	$146.20	$146.20
Purchase #2	$57.91	6.119%	$61.4535	$61.45	$61.45	$61.50
Purchase #3	$92.80	5.873%	$98.2501	$98.25	$98.25	$98.30
Purchase #4	$102.82	4.861%	$107.8181	$107.82	$107.80	$107.80
Purchase #5	$41.26	13.723%	$46.9221	$46.92	$46.90	$46.90
Purchase #6	$213.41	4.162%	$222.2921	$222.29	$222.30	$222.30
Purchase #7	$188.81	12.668%	$212.7285	$212.73	$212.75	$212.70
7 purchase totals =	$828.52		$895.6798	$895.68	$895.65	$895.70