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	$208.55	11.495%	$232.5228	$232.52	$232.50	$232.50
Purchase #2	$93.89	3.547%	$97.2203	$97.22	$97.20	$97.20
Purchase #3	$27.63	4.421%	$28.8515	$28.85	$28.85	$28.90
Purchase #4	$230.99	10.185%	$254.5163	$254.52	$254.50	$254.50
Purchase #5	$56.40	5.282%	$59.379	$59.38	$59.40	$59.40
Purchase #6	$174.47	11.725%	$194.9266	$194.93	$194.95	$194.90
Purchase #7	$55.78	10.182%	$61.4595	$61.46	$61.45	$61.50
7 purchase totals =	$847.71		$928.8760	$928.88	$928.85	$928.90