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	$6.87	5.853%	$7.2721	$7.27	$7.25	$7.30
Purchase #2	$12.87	13.356%	$14.5889	$14.59	$14.60	$14.60
Purchase #3	$244.85	6.837%	$261.5904	$261.59	$261.60	$261.60
Purchase #4	$216.37	5.508%	$228.2877	$228.29	$228.30	$228.30
Purchase #5	$88.54	13.613%	$100.593	$100.59	$100.60	$100.60
Purchase #6	$10.56	4.121%	$10.9952	$11.00	$11.00	$11.00
Purchase #7	$81.81	8.827%	$89.0314	$89.03	$89.05	$89.00
7 purchase totals =	$661.87		$712.3587	$712.36	$712.40	$712.40