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	$209.91	8.716%	$228.2058	$228.21	$228.20	$228.20
Purchase #2	$137.76	11.864%	$154.1038	$154.10	$154.10	$154.10
Purchase #3	$224.60	12.158%	$251.9069	$251.91	$251.90	$251.90
Purchase #4	$53.50	10.485%	$59.1095	$59.11	$59.10	$59.10
Purchase #5	$103.41	7.812%	$111.4884	$111.49	$111.50	$111.50
Purchase #6	$89.93	6.150%	$95.4607	$95.46	$95.45	$95.50
Purchase #7	$232.32	9.324%	$253.9815	$253.98	$254.00	$254.00
7 purchase totals =	$1,051.43		$1,154.2566	$1,154.26	$1,154.25	$1,154.30