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	$133.53	6.399%	$142.0746	$142.07	$142.05	$142.10
Purchase #2	$48.43	6.105%	$51.3867	$51.39	$51.40	$51.40
Purchase #3	$216.89	8.530%	$235.3907	$235.39	$235.40	$235.40
Purchase #4	$103.67	4.733%	$108.5767	$108.58	$108.60	$108.60
Purchase #5	$131.77	11.847%	$147.3808	$147.38	$147.40	$147.40
Purchase #6	$234.81	4.576%	$245.5549	$245.55	$245.55	$245.60
Purchase #7	$82.74	7.461%	$88.9132	$88.91	$88.90	$88.90
7 purchase totals =	$951.84		$1,019.2776	$1,019.27	$1,019.30	$1,019.40