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	$199.88	11.592%	$223.0501	$223.05	$223.05	$223.10
Purchase #2	$30.37	11.754%	$33.9397	$33.94	$33.95	$33.90
Purchase #3	$142.55	10.289%	$157.217	$157.22	$157.20	$157.20
Purchase #4	$201.55	10.390%	$222.491	$222.49	$222.50	$222.50
Purchase #5	$97.49	12.400%	$109.5788	$109.58	$109.60	$109.60
Purchase #6	$37.25	3.620%	$38.5985	$38.60	$38.60	$38.60
Purchase #7	$123.32	7.643%	$132.7453	$132.75	$132.75	$132.70
7 purchase totals =	$832.41		$917.6204	$917.63	$917.65	$917.60