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	$149.46	4.270%	$155.8419	$155.84	$155.85	$155.80
Purchase #2	$115.35	11.482%	$128.5945	$128.59	$128.60	$128.60
Purchase #3	$123.66	3.284%	$127.721	$127.72	$127.70	$127.70
Purchase #4	$196.55	13.726%	$223.5285	$223.53	$223.55	$223.50
Purchase #5	$104.72	12.745%	$118.0666	$118.07	$118.05	$118.10
Purchase #6	$7.32	7.829%	$7.8931	$7.89	$7.90	$7.90
Purchase #7	$139.71	9.849%	$153.47	$153.47	$153.45	$153.50
7 purchase totals =	$836.77		$915.1156	$915.11	$915.10	$915.10