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	$111.56	6.519%	$118.8326	$118.83	$118.85	$118.80
Purchase #2	$145.94	13.853%	$166.1571	$166.16	$166.15	$166.20
Purchase #3	$14.45	12.548%	$16.2632	$16.26	$16.25	$16.30
Purchase #4	$249.26	5.871%	$263.8941	$263.89	$263.90	$263.90
Purchase #5	$75.38	10.301%	$83.1449	$83.14	$83.15	$83.10
Purchase #6	$65.29	9.835%	$71.7113	$71.71	$71.70	$71.70
Purchase #7	$206.47	7.639%	$222.2422	$222.24	$222.25	$222.20
7 purchase totals =	$868.35		$942.2454	$942.23	$942.25	$942.20