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	$76.67	8.817%	$83.43	$83.43	$83.45	$83.40
Purchase #2	$139.31	8.851%	$151.6403	$151.64	$151.65	$151.60
Purchase #3	$243.84	3.387%	$252.0989	$252.10	$252.10	$252.10
Purchase #4	$162.77	3.490%	$168.4507	$168.45	$168.45	$168.50
Purchase #5	$210.29	9.798%	$230.8942	$230.89	$230.90	$230.90
Purchase #6	$222.51	13.503%	$252.5555	$252.56	$252.55	$252.60
Purchase #7	$41.71	9.788%	$45.7926	$45.79	$45.80	$45.80
7 purchase totals =	$1,097.10		$1,184.8622	$1,184.86	$1,184.90	$1,184.90