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	$32.65	13.535%	$37.0692	$37.07	$37.05	$37.10
Purchase #2	$190.35	11.709%	$212.6381	$212.64	$212.65	$212.60
Purchase #3	$58.54	4.353%	$61.0882	$61.09	$61.10	$61.10
Purchase #4	$153.89	8.666%	$167.2261	$167.23	$167.25	$167.20
Purchase #5	$69.25	5.473%	$73.0401	$73.04	$73.05	$73.00
Purchase #6	$184.82	3.676%	$191.614	$191.61	$191.60	$191.60
Purchase #7	$17.37	6.203%	$18.4475	$18.45	$18.45	$18.40
7 purchase totals =	$706.87		$761.1232	$761.13	$761.15	$761.00