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	$111.52	13.467%	$126.5384	$126.54	$126.55	$126.50
Purchase #2	$42.34	7.860%	$45.6679	$45.67	$45.65	$45.70
Purchase #3	$117.38	8.385%	$127.2223	$127.22	$127.20	$127.20
Purchase #4	$81.63	11.113%	$90.7015	$90.70	$90.70	$90.70
Purchase #5	$60.52	10.638%	$66.9581	$66.96	$66.95	$67.00
Purchase #6	$203.76	10.857%	$225.8822	$225.88	$225.90	$225.90
Purchase #7	$67.91	10.418%	$74.9849	$74.98	$75.00	$75.00
7 purchase totals =	$685.06		$757.9553	$757.95	$757.95	$758.00