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	$29.45	10.609%	$32.5744	$32.57	$32.55	$32.60
Purchase #2	$54.96	3.785%	$57.0402	$57.04	$57.05	$57.00
Purchase #3	$82.90	13.336%	$93.9555	$93.96	$93.95	$94.00
Purchase #4	$214.89	8.833%	$233.8712	$233.87	$233.85	$233.90
Purchase #5	$141.69	13.838%	$161.2971	$161.30	$161.30	$161.30
Purchase #6	$40.52	13.391%	$45.946	$45.95	$45.95	$45.90
Purchase #7	$90.58	10.270%	$99.8826	$99.88	$99.90	$99.90
7 purchase totals =	$654.99		$724.5670	$724.57	$724.55	$724.60