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	$216.91	4.121%	$225.8489	$225.85	$225.85	$225.80
Purchase #2	$193.66	12.873%	$218.5899	$218.59	$218.60	$218.60
Purchase #3	$131.74	9.168%	$143.8179	$143.82	$143.80	$143.80
Purchase #4	$202.62	5.412%	$213.5858	$213.59	$213.60	$213.60
Purchase #5	$52.81	8.319%	$57.2033	$57.20	$57.20	$57.20
Purchase #6	$48.39	13.432%	$54.8897	$54.89	$54.90	$54.90
Purchase #7	$34.71	11.223%	$38.6055	$38.61	$38.60	$38.60
7 purchase totals =	$880.84		$952.5410	$952.55	$952.55	$952.50