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	$239.44	13.380%	$271.4771	$271.48	$271.50	$271.50
Purchase #2	$20.45	5.260%	$21.5257	$21.53	$21.55	$21.50
Purchase #3	$18.48	11.765%	$20.6542	$20.65	$20.65	$20.70
Purchase #4	$132.58	7.371%	$142.3525	$142.35	$142.35	$142.40
Purchase #5	$50.72	5.760%	$53.6415	$53.64	$53.65	$53.60
Purchase #6	$171.54	8.225%	$185.6492	$185.65	$185.65	$185.60
Purchase #7	$34.58	9.429%	$37.8405	$37.84	$37.85	$37.80
7 purchase totals =	$667.79		$733.1407	$733.14	$733.20	$733.10