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	$213.77	5.390%	$225.2922	$225.29	$225.30	$225.30
Purchase #2	$38.59	7.830%	$41.6116	$41.61	$41.60	$41.60
Purchase #3	$187.41	13.239%	$212.2212	$212.22	$212.20	$212.20
Purchase #4	$55.96	6.630%	$59.6701	$59.67	$59.65	$59.70
Purchase #5	$34.59	7.179%	$37.0732	$37.07	$37.05	$37.10
Purchase #6	$157.45	8.849%	$171.3828	$171.38	$171.40	$171.40
Purchase #7	$78.26	10.307%	$86.3263	$86.33	$86.35	$86.30
7 purchase totals =	$766.03		$833.5774	$833.57	$833.55	$833.60