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	$58.91	6.514%	$62.7474	$62.75	$62.75	$62.70
Purchase #2	$156.54	7.569%	$168.3885	$168.39	$168.40	$168.40
Purchase #3	$44.66	12.203%	$50.1099	$50.11	$50.10	$50.10
Purchase #4	$125.81	4.508%	$131.4815	$131.48	$131.50	$131.50
Purchase #5	$151.49	11.734%	$169.2658	$169.27	$169.25	$169.30
Purchase #6	$13.51	10.647%	$14.9484	$14.95	$14.95	$14.90
Purchase #7	$131.56	7.369%	$141.2547	$141.25	$141.25	$141.30
7 purchase totals =	$682.48		$738.1962	$738.20	$738.20	$738.20