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	$99.52	12.753%	$112.2118	$112.21	$112.20	$112.20
Purchase #2	$74.43	4.496%	$77.7764	$77.78	$77.80	$77.80
Purchase #3	$33.79	12.114%	$37.8833	$37.88	$37.90	$37.90
Purchase #4	$216.82	5.832%	$229.4649	$229.46	$229.45	$229.50
Purchase #5	$58.87	5.870%	$62.3257	$62.33	$62.35	$62.30
Purchase #6	$161.90	5.644%	$171.0376	$171.04	$171.05	$171.00
Purchase #7	$64.26	6.863%	$68.6702	$68.67	$68.65	$68.70
7 purchase totals =	$709.59		$759.3699	$759.37	$759.40	$759.40