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	$113.28	8.459%	$122.8624	$122.86	$122.85	$122.90
Purchase #2	$231.90	9.710%	$254.4175	$254.42	$254.40	$254.40
Purchase #3	$138.50	9.521%	$151.6866	$151.69	$151.70	$151.70
Purchase #4	$157.67	12.169%	$176.8569	$176.86	$176.85	$176.90
Purchase #5	$101.50	9.521%	$111.1638	$111.16	$111.15	$111.20
Purchase #6	$32.35	4.785%	$33.8979	$33.90	$33.90	$33.90
Purchase #7	$139.72	10.306%	$154.1195	$154.12	$154.10	$154.10
7 purchase totals =	$914.92		$1,005.0046	$1,005.01	$1,004.95	$1,005.10