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	$93.48	8.398%	$101.3305	$101.33	$101.35	$101.30
Purchase #2	$61.88	7.372%	$66.4418	$66.44	$66.45	$66.40
Purchase #3	$93.42	7.560%	$100.4826	$100.48	$100.50	$100.50
Purchase #4	$123.40	11.559%	$137.6638	$137.66	$137.65	$137.70
Purchase #5	$11.74	9.870%	$12.8987	$12.90	$12.90	$12.90
Purchase #6	$198.61	4.836%	$208.2148	$208.21	$208.20	$208.20
Purchase #7	$89.89	6.778%	$95.9827	$95.98	$96.00	$96.00
7 purchase totals =	$672.42		$723.0149	$723.00	$723.05	$723.00