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	$38.45	4.867%	$40.3214	$40.32	$40.30	$40.30
Purchase #2	$68.87	3.279%	$71.1282	$71.13	$71.15	$71.10
Purchase #3	$89.71	5.345%	$94.505	$94.51	$94.50	$94.50
Purchase #4	$231.52	7.756%	$249.4767	$249.48	$249.50	$249.50
Purchase #5	$204.78	13.368%	$232.155	$232.16	$232.15	$232.20
Purchase #6	$107.48	3.766%	$111.5277	$111.53	$111.55	$111.50
Purchase #7	$71.94	7.393%	$77.2585	$77.26	$77.25	$77.30
7 purchase totals =	$812.75		$876.3725	$876.39	$876.40	$876.40