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	$85.40	6.495%	$90.9467	$90.95	$90.95	$90.90
Purchase #2	$120.54	13.244%	$136.5043	$136.50	$136.50	$136.50
Purchase #3	$241.53	12.543%	$271.8251	$271.83	$271.85	$271.80
Purchase #4	$210.29	13.623%	$238.9378	$238.94	$238.95	$238.90
Purchase #5	$34.97	12.183%	$39.2304	$39.23	$39.25	$39.20
Purchase #6	$141.70	10.340%	$156.3518	$156.35	$156.35	$156.40
Purchase #7	$193.98	6.414%	$206.4219	$206.42	$206.40	$206.40
7 purchase totals =	$1,028.41		$1,140.2180	$1,140.22	$1,140.25	$1,140.10