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	$77.27	6.294%	$82.1334	$82.13	$82.15	$82.10
Purchase #2	$90.62	10.555%	$100.1849	$100.18	$100.20	$100.20
Purchase #3	$137.81	13.377%	$156.2448	$156.24	$156.25	$156.20
Purchase #4	$50.74	4.238%	$52.8904	$52.89	$52.90	$52.90
Purchase #5	$202.29	10.537%	$223.6053	$223.61	$223.60	$223.60
Purchase #6	$220.48	6.824%	$235.5256	$235.53	$235.55	$235.50
Purchase #7	$184.46	4.164%	$192.1409	$192.14	$192.15	$192.10
7 purchase totals =	$963.67		$1,042.7253	$1,042.72	$1,042.80	$1,042.60