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	$167.85	6.854%	$179.3544	$179.35	$179.35	$179.40
Purchase #2	$230.83	11.104%	$256.4614	$256.46	$256.45	$256.50
Purchase #3	$172.71	10.266%	$190.4404	$190.44	$190.45	$190.40
Purchase #4	$7.66	4.482%	$8.0033	$8.00	$8.00	$8.00
Purchase #5	$22.71	7.439%	$24.3994	$24.40	$24.40	$24.40
Purchase #6	$167.39	13.354%	$189.7433	$189.74	$189.75	$189.70
Purchase #7	$56.27	10.857%	$62.3792	$62.38	$62.40	$62.40
7 purchase totals =	$825.42		$910.7814	$910.77	$910.80	$910.80