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	$218.58	6.518%	$232.827	$232.83	$232.85	$232.80
Purchase #2	$31.36	12.573%	$35.3029	$35.30	$35.30	$35.30
Purchase #3	$208.47	7.158%	$223.3923	$223.39	$223.40	$223.40
Purchase #4	$132.69	8.733%	$144.2778	$144.28	$144.30	$144.30
Purchase #5	$36.56	10.305%	$40.3275	$40.33	$40.35	$40.30
Purchase #6	$117.77	10.655%	$130.3184	$130.32	$130.30	$130.30
Purchase #7	$249.57	9.814%	$274.0628	$274.06	$274.05	$274.10
7 purchase totals =	$995.00		$1,080.5087	$1,080.51	$1,080.55	$1,080.50