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	$197.94	12.763%	$223.2031	$223.20	$223.20	$223.20
Purchase #2	$203.53	3.817%	$211.2987	$211.30	$211.30	$211.30
Purchase #3	$56.86	5.389%	$59.9242	$59.92	$59.90	$59.90
Purchase #4	$238.42	4.600%	$249.3873	$249.39	$249.40	$249.40
Purchase #5	$142.81	8.838%	$155.4315	$155.43	$155.45	$155.40
Purchase #6	$123.50	12.776%	$139.2784	$139.28	$139.30	$139.30
Purchase #7	$92.49	5.365%	$97.4521	$97.45	$97.45	$97.50
7 purchase totals =	$1,055.55		$1,135.9753	$1,135.97	$1,136.00	$1,136.00