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	$176.37	12.192%	$197.873	$197.87	$197.85	$197.90
Purchase #2	$22.95	7.215%	$24.6058	$24.61	$24.60	$24.60
Purchase #3	$65.62	11.578%	$73.2175	$73.22	$73.20	$73.20
Purchase #4	$238.97	11.785%	$267.1326	$267.13	$267.15	$267.10
Purchase #5	$175.63	11.745%	$196.2577	$196.26	$196.25	$196.30
Purchase #6	$18.93	8.621%	$20.562	$20.56	$20.55	$20.60
Purchase #7	$39.63	8.171%	$42.8682	$42.87	$42.85	$42.90
7 purchase totals =	$738.10		$822.5168	$822.52	$822.45	$822.60