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	$12.28	13.858%	$13.9818	$13.98	$14.00	$14.00
Purchase #2	$122.46	13.428%	$138.9039	$138.90	$138.90	$138.90
Purchase #3	$131.48	3.873%	$136.5722	$136.57	$136.55	$136.60
Purchase #4	$158.76	6.408%	$168.9333	$168.93	$168.95	$168.90
Purchase #5	$39.86	7.650%	$42.9093	$42.91	$42.90	$42.90
Purchase #6	$117.59	10.166%	$129.5442	$129.54	$129.55	$129.50
Purchase #7	$172.58	10.733%	$191.103	$191.10	$191.10	$191.10
7 purchase totals =	$755.01		$821.9477	$821.93	$821.95	$821.90