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	$40.49	12.240%	$45.446	$45.45	$45.45	$45.40
Purchase #2	$223.76	4.704%	$234.2857	$234.29	$234.30	$234.30
Purchase #3	$188.56	8.612%	$204.7988	$204.80	$204.80	$204.80
Purchase #4	$141.75	7.225%	$151.9914	$151.99	$152.00	$152.00
Purchase #5	$132.31	8.716%	$143.8421	$143.84	$143.85	$143.80
Purchase #6	$50.25	7.727%	$54.1328	$54.13	$54.15	$54.10
Purchase #7	$203.98	11.453%	$227.3418	$227.34	$227.35	$227.30
7 purchase totals =	$981.10		$1,061.8386	$1,061.84	$1,061.90	$1,061.70