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	$78.46	12.777%	$88.4848	$88.48	$88.50	$88.50
Purchase #2	$105.76	5.715%	$111.8042	$111.80	$111.80	$111.80
Purchase #3	$79.48	4.494%	$83.0518	$83.05	$83.05	$83.10
Purchase #4	$200.72	12.172%	$225.1516	$225.15	$225.15	$225.20
Purchase #5	$32.67	6.371%	$34.7514	$34.75	$34.75	$34.80
Purchase #6	$187.99	3.639%	$194.831	$194.83	$194.85	$194.80
Purchase #7	$127.79	5.268%	$134.522	$134.52	$134.50	$134.50
7 purchase totals =	$812.87		$872.5968	$872.58	$872.60	$872.70