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	$192.43	8.675%	$209.1233	$209.12	$209.10	$209.10
Purchase #2	$182.76	7.529%	$196.52	$196.52	$196.50	$196.50
Purchase #3	$78.87	5.733%	$83.3916	$83.39	$83.40	$83.40
Purchase #4	$133.83	4.471%	$139.8135	$139.81	$139.80	$139.80
Purchase #5	$158.40	7.618%	$170.4669	$170.47	$170.45	$170.50
Purchase #6	$200.25	11.598%	$223.475	$223.48	$223.50	$223.50
Purchase #7	$236.29	8.210%	$255.6894	$255.69	$255.70	$255.70
7 purchase totals =	$1,182.83		$1,278.4797	$1,278.48	$1,278.45	$1,278.50