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	$42.81	4.840%	$44.882	$44.88	$44.90	$44.90
Purchase #2	$248.77	10.152%	$274.0251	$274.03	$274.05	$274.00
Purchase #3	$37.95	6.738%	$40.5071	$40.51	$40.50	$40.50
Purchase #4	$55.69	3.317%	$57.5372	$57.54	$57.55	$57.50
Purchase #5	$63.77	12.244%	$71.578	$71.58	$71.60	$71.60
Purchase #6	$235.62	11.823%	$263.4774	$263.48	$263.50	$263.50
Purchase #7	$193.42	9.778%	$212.3326	$212.33	$212.35	$212.30
7 purchase totals =	$878.03		$964.3394	$964.35	$964.45	$964.30