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	$80.29	11.355%	$89.4069	$89.41	$89.40	$89.40
Purchase #2	$45.49	5.800%	$48.1284	$48.13	$48.15	$48.10
Purchase #3	$49.61	5.333%	$52.2557	$52.26	$52.25	$52.30
Purchase #4	$160.71	5.495%	$169.541	$169.54	$169.55	$169.50
Purchase #5	$151.90	13.831%	$172.9093	$172.91	$172.90	$172.90
Purchase #6	$83.83	11.613%	$93.5652	$93.57	$93.55	$93.60
Purchase #7	$77.27	12.817%	$87.1737	$87.17	$87.15	$87.20
7 purchase totals =	$649.10		$712.9802	$712.99	$712.95	$713.00