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	$50.39	13.338%	$57.111	$57.11	$57.10	$57.10
Purchase #2	$31.86	4.656%	$33.3434	$33.34	$33.35	$33.30
Purchase #3	$60.35	3.540%	$62.4864	$62.49	$62.50	$62.50
Purchase #4	$171.89	4.282%	$179.2503	$179.25	$179.25	$179.30
Purchase #5	$230.85	11.496%	$257.3885	$257.39	$257.40	$257.40
Purchase #6	$242.58	6.784%	$259.0366	$259.04	$259.05	$259.00
Purchase #7	$33.79	12.143%	$37.8931	$37.89	$37.90	$37.90
7 purchase totals =	$821.71		$886.5093	$886.51	$886.55	$886.50