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	$126.37	4.340%	$131.8545	$131.85	$131.85	$131.90
Purchase #2	$65.36	3.682%	$67.7666	$67.77	$67.75	$67.80
Purchase #3	$99.77	11.869%	$111.6117	$111.61	$111.60	$111.60
Purchase #4	$30.41	8.513%	$32.9988	$33.00	$33.00	$33.00
Purchase #5	$204.53	13.461%	$232.0618	$232.06	$232.05	$232.10
Purchase #6	$62.26	7.826%	$67.1325	$67.13	$67.15	$67.10
Purchase #7	$180.89	10.341%	$199.5958	$199.60	$199.60	$199.60
7 purchase totals =	$769.59		$843.0217	$843.02	$843.00	$843.10