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	$198.49	7.587%	$213.5494	$213.55	$213.55	$213.50
Purchase #2	$40.59	13.198%	$45.9471	$45.95	$45.95	$45.90
Purchase #3	$46.40	10.767%	$51.3959	$51.40	$51.40	$51.40
Purchase #4	$137.37	3.741%	$142.509	$142.51	$142.50	$142.50
Purchase #5	$51.33	10.546%	$56.7433	$56.74	$56.75	$56.70
Purchase #6	$230.89	13.761%	$262.6628	$262.66	$262.65	$262.70
Purchase #7	$66.67	13.660%	$75.7771	$75.78	$75.80	$75.80
7 purchase totals =	$771.74		$848.5846	$848.59	$848.60	$848.50