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	$118.51	8.139%	$128.1555	$128.16	$128.15	$128.20
Purchase #2	$177.50	12.554%	$199.7834	$199.78	$199.80	$199.80
Purchase #3	$188.67	6.479%	$200.8939	$200.89	$200.90	$200.90
Purchase #4	$152.72	7.425%	$164.0595	$164.06	$164.05	$164.10
Purchase #5	$140.78	10.469%	$155.5183	$155.52	$155.50	$155.50
Purchase #6	$88.95	6.769%	$94.971	$94.97	$94.95	$95.00
Purchase #7	$151.59	3.574%	$157.0078	$157.01	$157.00	$157.00
7 purchase totals =	$1,018.72		$1,100.3894	$1,100.39	$1,100.35	$1,100.50