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	$36.73	3.322%	$37.9502	$37.95	$37.95	$38.00
Purchase #2	$93.87	7.121%	$100.5545	$100.55	$100.55	$100.60
Purchase #3	$113.61	9.666%	$124.5915	$124.59	$124.60	$124.60
Purchase #4	$155.88	7.687%	$167.8625	$167.86	$167.85	$167.90
Purchase #5	$249.53	10.399%	$275.4786	$275.48	$275.50	$275.50
Purchase #6	$248.32	9.329%	$271.4858	$271.49	$271.50	$271.50
Purchase #7	$122.87	7.569%	$132.17	$132.17	$132.15	$132.20
7 purchase totals =	$1,020.81		$1,110.0931	$1,110.09	$1,110.10	$1,110.30