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	$177.87	13.384%	$201.6761	$201.68	$201.70	$201.70
Purchase #2	$37.39	13.503%	$42.4388	$42.44	$42.45	$42.40
Purchase #3	$137.41	5.865%	$145.4691	$145.47	$145.45	$145.50
Purchase #4	$34.78	7.781%	$37.4862	$37.49	$37.50	$37.50
Purchase #5	$147.89	13.692%	$168.1391	$168.14	$168.15	$168.10
Purchase #6	$245.61	7.674%	$264.4581	$264.46	$264.45	$264.50
Purchase #7	$126.53	8.650%	$137.4748	$137.47	$137.45	$137.50
7 purchase totals =	$907.48		$997.1422	$997.15	$997.15	$997.20