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	$213.34	10.162%	$235.0196	$235.02	$235.00	$235.00
Purchase #2	$189.83	9.735%	$208.31	$208.31	$208.30	$208.30
Purchase #3	$77.65	9.613%	$85.1145	$85.11	$85.10	$85.10
Purchase #4	$138.36	9.473%	$151.4668	$151.47	$151.45	$151.50
Purchase #5	$235.46	5.249%	$247.8193	$247.82	$247.80	$247.80
Purchase #6	$104.64	13.135%	$118.3845	$118.38	$118.40	$118.40
Purchase #7	$152.96	10.157%	$168.4961	$168.50	$168.50	$168.50
7 purchase totals =	$1,112.24		$1,214.6108	$1,214.61	$1,214.55	$1,214.60