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	$239.70	13.686%	$272.5053	$272.51	$272.50	$272.50
Purchase #2	$71.39	7.168%	$76.5072	$76.51	$76.50	$76.50
Purchase #3	$138.77	13.419%	$157.3915	$157.39	$157.40	$157.40
Purchase #4	$152.29	12.672%	$171.5882	$171.59	$171.60	$171.60
Purchase #5	$37.53	12.579%	$42.2509	$42.25	$42.25	$42.30
Purchase #6	$203.93	11.496%	$227.3738	$227.37	$227.35	$227.40
Purchase #7	$211.61	10.550%	$233.9349	$233.93	$233.95	$233.90
7 purchase totals =	$1,055.22		$1,181.5518	$1,181.55	$1,181.55	$1,181.60