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	$62.37	8.301%	$67.5473	$67.55	$67.55	$67.50
Purchase #2	$213.42	12.487%	$240.0698	$240.07	$240.05	$240.10
Purchase #3	$47.45	10.390%	$52.3801	$52.38	$52.40	$52.40
Purchase #4	$216.72	11.469%	$241.5756	$241.58	$241.60	$241.60
Purchase #5	$62.94	3.858%	$65.3682	$65.37	$65.35	$65.40
Purchase #6	$65.49	8.496%	$71.054	$71.05	$71.05	$71.10
Purchase #7	$142.60	5.659%	$150.6697	$150.67	$150.65	$150.70
7 purchase totals =	$810.99		$888.6647	$888.67	$888.65	$888.80