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	$43.93	11.120%	$48.815	$48.82	$48.80	$48.80
Purchase #2	$195.52	13.568%	$222.0482	$222.05	$222.05	$222.00
Purchase #3	$194.67	10.817%	$215.7275	$215.73	$215.75	$215.70
Purchase #4	$172.89	4.417%	$180.5266	$180.53	$180.55	$180.50
Purchase #5	$44.58	3.624%	$46.1956	$46.20	$46.20	$46.20
Purchase #6	$77.43	6.711%	$82.6263	$82.63	$82.65	$82.60
Purchase #7	$35.86	5.644%	$37.8839	$37.88	$37.90	$37.90
7 purchase totals =	$764.88		$833.8231	$833.84	$833.90	$833.70