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	$220.61	11.738%	$246.5052	$246.51	$246.50	$246.50
Purchase #2	$149.26	3.495%	$154.4766	$154.48	$154.50	$154.50
Purchase #3	$115.59	12.614%	$130.1705	$130.17	$130.15	$130.20
Purchase #4	$124.91	12.449%	$140.46	$140.46	$140.45	$140.50
Purchase #5	$116.55	11.832%	$130.3402	$130.34	$130.35	$130.30
Purchase #6	$41.73	8.598%	$45.3179	$45.32	$45.30	$45.30
Purchase #7	$228.80	5.164%	$240.6152	$240.62	$240.60	$240.60
7 purchase totals =	$997.45		$1,087.8856	$1,087.90	$1,087.85	$1,087.90