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	$239.60	4.695%	$250.8492	$250.85	$250.85	$250.80
Purchase #2	$213.70	13.723%	$243.0261	$243.03	$243.05	$243.00
Purchase #3	$33.78	13.606%	$38.3761	$38.38	$38.40	$38.40
Purchase #4	$42.32	7.417%	$45.4589	$45.46	$45.45	$45.50
Purchase #5	$128.77	8.116%	$139.221	$139.22	$139.20	$139.20
Purchase #6	$206.58	11.751%	$230.8552	$230.86	$230.85	$230.90
Purchase #7	$7.34	3.285%	$7.5811	$7.58	$7.60	$7.60
7 purchase totals =	$872.09		$955.3676	$955.38	$955.40	$955.40