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	$61.73	5.528%	$65.1424	$65.14	$65.15	$65.10
Purchase #2	$224.85	7.227%	$241.0999	$241.10	$241.10	$241.10
Purchase #3	$226.80	8.387%	$245.8217	$245.82	$245.80	$245.80
Purchase #4	$123.37	6.682%	$131.6136	$131.61	$131.60	$131.60
Purchase #5	$193.64	8.303%	$209.7179	$209.72	$209.70	$209.70
Purchase #6	$225.48	13.766%	$256.5196	$256.52	$256.50	$256.50
Purchase #7	$189.85	12.331%	$213.2604	$213.26	$213.25	$213.30
7 purchase totals =	$1,245.72		$1,363.1755	$1,363.17	$1,363.10	$1,363.10