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	$133.81	8.503%	$145.1879	$145.19	$145.20	$145.20
Purchase #2	$118.30	7.705%	$127.415	$127.42	$127.40	$127.40
Purchase #3	$141.49	8.695%	$153.7926	$153.79	$153.80	$153.80
Purchase #4	$155.84	10.602%	$172.3622	$172.36	$172.35	$172.40
Purchase #5	$82.37	8.677%	$89.5172	$89.52	$89.50	$89.50
Purchase #6	$135.54	10.252%	$149.4356	$149.44	$149.45	$149.40
Purchase #7	$154.34	9.665%	$169.257	$169.26	$169.25	$169.30
7 purchase totals =	$921.69		$1,006.9675	$1,006.98	$1,006.95	$1,007.00