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	$35.57	6.711%	$37.9571	$37.96	$37.95	$38.00
Purchase #2	$55.82	9.792%	$61.2859	$61.29	$61.30	$61.30
Purchase #3	$29.42	9.372%	$32.1772	$32.18	$32.20	$32.20
Purchase #4	$50.50	3.503%	$52.269	$52.27	$52.25	$52.30
Purchase #5	$93.70	9.162%	$102.2848	$102.28	$102.30	$102.30
Purchase #6	$96.33	5.761%	$101.8796	$101.88	$101.90	$101.90
Purchase #7	$199.28	11.201%	$221.6014	$221.60	$221.60	$221.60
7 purchase totals =	$560.62		$609.4550	$609.46	$609.50	$609.60