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	$12.30	7.873%	$13.2684	$13.27	$13.25	$13.30
Purchase #2	$126.57	4.168%	$131.8454	$131.85	$131.85	$131.80
Purchase #3	$193.51	8.746%	$210.4344	$210.43	$210.45	$210.40
Purchase #4	$172.91	12.757%	$194.9681	$194.97	$194.95	$195.00
Purchase #5	$65.74	11.279%	$73.1548	$73.15	$73.15	$73.20
Purchase #6	$148.37	11.164%	$164.934	$164.93	$164.95	$164.90
Purchase #7	$239.46	7.241%	$256.7993	$256.80	$256.80	$256.80
7 purchase totals =	$958.86		$1,045.4044	$1,045.40	$1,045.40	$1,045.40