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	$225.38	10.776%	$249.6669	$249.67	$249.65	$249.70
Purchase #2	$52.89	8.340%	$57.301	$57.30	$57.30	$57.30
Purchase #3	$149.50	3.832%	$155.2288	$155.23	$155.25	$155.20
Purchase #4	$176.66	13.258%	$200.0816	$200.08	$200.10	$200.10
Purchase #5	$65.48	10.666%	$72.4641	$72.46	$72.45	$72.50
Purchase #6	$234.55	4.262%	$244.5465	$244.55	$244.55	$244.50
Purchase #7	$250.52	9.770%	$274.9958	$275.00	$275.00	$275.00
7 purchase totals =	$1,154.98		$1,254.2847	$1,254.29	$1,254.30	$1,254.30