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	$153.97	8.103%	$166.4462	$166.45	$166.45	$166.40
Purchase #2	$95.97	12.188%	$107.6668	$107.67	$107.65	$107.70
Purchase #3	$189.47	3.781%	$196.6339	$196.63	$196.65	$196.60
Purchase #4	$243.77	5.388%	$256.9043	$256.90	$256.90	$256.90
Purchase #5	$50.31	13.722%	$57.2135	$57.21	$57.20	$57.20
Purchase #6	$101.50	3.588%	$105.1418	$105.14	$105.15	$105.10
Purchase #7	$40.89	3.123%	$42.167	$42.17	$42.15	$42.20
7 purchase totals =	$875.88		$932.1735	$932.17	$932.15	$932.10