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	$213.31	13.296%	$241.6717	$241.67	$241.65	$241.70
Purchase #2	$104.69	12.295%	$117.5616	$117.56	$117.55	$117.60
Purchase #3	$77.33	6.440%	$82.3101	$82.31	$82.30	$82.30
Purchase #4	$224.77	12.674%	$253.2573	$253.26	$253.25	$253.30
Purchase #5	$90.79	12.533%	$102.1687	$102.17	$102.15	$102.20
Purchase #6	$75.36	13.446%	$85.4929	$85.49	$85.50	$85.50
Purchase #7	$160.89	8.792%	$175.0354	$175.04	$175.05	$175.00
7 purchase totals =	$947.14		$1,057.4977	$1,057.50	$1,057.45	$1,057.60