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	$51.46	11.650%	$57.4551	$57.46	$57.45	$57.50
Purchase #2	$17.25	11.679%	$19.2646	$19.26	$19.25	$19.30
Purchase #3	$247.39	9.110%	$269.9272	$269.93	$269.95	$269.90
Purchase #4	$193.28	6.522%	$205.8857	$205.89	$205.90	$205.90
Purchase #5	$103.25	5.487%	$108.9153	$108.92	$108.90	$108.90
Purchase #6	$139.37	12.458%	$156.7327	$156.73	$156.75	$156.70
Purchase #7	$195.88	13.735%	$222.7841	$222.78	$222.80	$222.80
7 purchase totals =	$947.88		$1,040.9647	$1,040.97	$1,041.00	$1,041.00