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	$75.86	7.580%	$81.6102	$81.61	$81.60	$81.60
Purchase #2	$53.45	11.474%	$59.5829	$59.58	$59.60	$59.60
Purchase #3	$31.91	7.518%	$34.309	$34.31	$34.30	$34.30
Purchase #4	$36.72	7.433%	$39.4494	$39.45	$39.45	$39.40
Purchase #5	$35.37	3.277%	$36.5291	$36.53	$36.55	$36.50
Purchase #6	$36.52	3.774%	$37.8983	$37.90	$37.90	$37.90
Purchase #7	$140.85	6.103%	$149.4461	$149.45	$149.45	$149.40
7 purchase totals =	$410.68		$438.8250	$438.83	$438.85	$438.70