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	$236.47	7.192%	$253.4769	$253.48	$253.50	$253.50
Purchase #2	$43.59	5.697%	$46.0733	$46.07	$46.05	$46.10
Purchase #3	$227.58	10.629%	$251.7695	$251.77	$251.75	$251.80
Purchase #4	$249.76	10.418%	$275.78	$275.78	$275.80	$275.80
Purchase #5	$200.39	5.293%	$210.9966	$211.00	$211.00	$211.00
Purchase #6	$86.25	10.679%	$95.4606	$95.46	$95.45	$95.50
Purchase #7	$40.45	12.703%	$45.5884	$45.59	$45.60	$45.60
7 purchase totals =	$1,084.49		$1,179.1453	$1,179.15	$1,179.15	$1,179.30