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	$130.67	7.322%	$140.2377	$140.24	$140.25	$140.20
Purchase #2	$18.86	10.159%	$20.776	$20.78	$20.80	$20.80
Purchase #3	$208.31	6.649%	$222.1605	$222.16	$222.15	$222.20
Purchase #4	$15.83	13.422%	$17.9547	$17.95	$17.95	$18.00
Purchase #5	$21.55	5.188%	$22.668	$22.67	$22.65	$22.70
Purchase #6	$238.89	11.523%	$266.4173	$266.42	$266.40	$266.40
Purchase #7	$175.49	12.207%	$196.9121	$196.91	$196.90	$196.90
7 purchase totals =	$809.60		$887.1263	$887.13	$887.10	$887.20