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	$195.43	7.382%	$209.8566	$209.86	$209.85	$209.90
Purchase #2	$197.80	13.806%	$225.1083	$225.11	$225.10	$225.10
Purchase #3	$9.82	4.686%	$10.2802	$10.28	$10.30	$10.30
Purchase #4	$173.30	12.765%	$195.4217	$195.42	$195.40	$195.40
Purchase #5	$87.63	3.238%	$90.4675	$90.47	$90.45	$90.50
Purchase #6	$37.30	12.688%	$42.0326	$42.03	$42.05	$42.00
Purchase #7	$203.32	8.363%	$220.3237	$220.32	$220.30	$220.30
7 purchase totals =	$904.60		$993.4906	$993.49	$993.45	$993.50