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	$146.64	3.192%	$151.3207	$151.32	$151.30	$151.30
Purchase #2	$131.34	13.219%	$148.7018	$148.70	$148.70	$148.70
Purchase #3	$236.71	8.465%	$256.7475	$256.75	$256.75	$256.70
Purchase #4	$34.66	10.809%	$38.4064	$38.41	$38.40	$38.40
Purchase #5	$72.47	6.709%	$77.332	$77.33	$77.35	$77.30
Purchase #6	$80.59	12.464%	$90.6347	$90.63	$90.65	$90.60
Purchase #7	$28.82	11.137%	$32.0297	$32.03	$32.05	$32.00
7 purchase totals =	$731.23		$795.1728	$795.17	$795.20	$795.00