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	$224.54	7.600%	$241.605	$241.61	$241.60	$241.60
Purchase #2	$210.93	11.753%	$235.7206	$235.72	$235.70	$235.70
Purchase #3	$83.40	8.256%	$90.2855	$90.29	$90.30	$90.30
Purchase #4	$131.26	11.680%	$146.5912	$146.59	$146.60	$146.60
Purchase #5	$41.52	11.632%	$46.3496	$46.35	$46.35	$46.30
Purchase #6	$55.35	7.187%	$59.328	$59.33	$59.35	$59.30
Purchase #7	$28.87	11.143%	$32.087	$32.09	$32.10	$32.10
7 purchase totals =	$775.87		$851.9669	$851.98	$852.00	$851.90