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	$5.88	3.244%	$6.0707	$6.07	$6.05	$6.10
Purchase #2	$232.31	10.358%	$256.3727	$256.37	$256.35	$256.40
Purchase #3	$250.78	11.439%	$279.4667	$279.47	$279.45	$279.50
Purchase #4	$173.93	9.514%	$190.4777	$190.48	$190.50	$190.50
Purchase #5	$222.44	8.223%	$240.7312	$240.73	$240.75	$240.70
Purchase #6	$219.33	6.492%	$233.5689	$233.57	$233.55	$233.60
Purchase #7	$159.85	4.277%	$166.6868	$166.69	$166.70	$166.70
7 purchase totals =	$1,264.52		$1,373.3747	$1,373.38	$1,373.35	$1,373.50