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	$57.37	9.499%	$62.8196	$62.82	$62.80	$62.80
Purchase #2	$56.91	4.165%	$59.2803	$59.28	$59.30	$59.30
Purchase #3	$73.88	6.544%	$78.7147	$78.71	$78.70	$78.70
Purchase #4	$159.81	8.854%	$173.9596	$173.96	$173.95	$174.00
Purchase #5	$188.57	12.753%	$212.6183	$212.62	$212.60	$212.60
Purchase #6	$108.44	12.806%	$122.3268	$122.33	$122.35	$122.30
Purchase #7	$110.91	7.105%	$118.7902	$118.79	$118.80	$118.80
7 purchase totals =	$755.89		$828.5095	$828.51	$828.50	$828.50