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	$66.75	7.508%	$71.7616	$71.76	$71.75	$71.80
Purchase #2	$153.41	9.518%	$168.0116	$168.01	$168.00	$168.00
Purchase #3	$242.73	8.588%	$263.5757	$263.58	$263.60	$263.60
Purchase #4	$134.32	10.552%	$148.4934	$148.49	$148.50	$148.50
Purchase #5	$13.82	9.821%	$15.1773	$15.18	$15.20	$15.20
Purchase #6	$33.52	12.124%	$37.584	$37.58	$37.60	$37.60
Purchase #7	$112.86	6.135%	$119.784	$119.78	$119.80	$119.80
7 purchase totals =	$757.41		$824.3876	$824.38	$824.45	$824.50