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	$43.29	12.543%	$48.7199	$48.72	$48.70	$48.70
Purchase #2	$227.65	8.873%	$247.8494	$247.85	$247.85	$247.80
Purchase #3	$196.81	7.446%	$211.4645	$211.46	$211.45	$211.50
Purchase #4	$229.86	11.569%	$256.4525	$256.45	$256.45	$256.50
Purchase #5	$134.46	7.440%	$144.4638	$144.46	$144.45	$144.50
Purchase #6	$171.49	6.168%	$182.0675	$182.07	$182.05	$182.10
Purchase #7	$95.91	6.246%	$101.9005	$101.90	$101.90	$101.90
7 purchase totals =	$1,099.47		$1,192.9181	$1,192.91	$1,192.85	$1,193.00