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	$127.82	11.601%	$142.6484	$142.65	$142.65	$142.60
Purchase #2	$127.79	9.107%	$139.4278	$139.43	$139.45	$139.40
Purchase #3	$165.82	3.597%	$171.7845	$171.78	$171.80	$171.80
Purchase #4	$20.84	4.677%	$21.8147	$21.81	$21.80	$21.80
Purchase #5	$112.95	5.496%	$119.1577	$119.16	$119.15	$119.20
Purchase #6	$223.51	9.231%	$244.1422	$244.14	$244.15	$244.10
Purchase #7	$99.26	9.298%	$108.4892	$108.49	$108.50	$108.50
7 purchase totals =	$877.99		$947.4645	$947.46	$947.50	$947.40