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	$140.52	4.517%	$146.8673	$146.87	$146.85	$146.90
Purchase #2	$34.45	4.308%	$35.9341	$35.93	$35.95	$35.90
Purchase #3	$97.86	10.539%	$108.1735	$108.17	$108.15	$108.20
Purchase #4	$242.54	12.510%	$272.8818	$272.88	$272.90	$272.90
Purchase #5	$108.39	7.814%	$116.8596	$116.86	$116.85	$116.90
Purchase #6	$33.34	8.148%	$36.0565	$36.06	$36.05	$36.10
Purchase #7	$142.31	12.496%	$160.0931	$160.09	$160.10	$160.10
7 purchase totals =	$799.41		$876.8659	$876.86	$876.85	$877.00