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	$76.62	12.115%	$85.9025	$85.90	$85.90	$85.90
Purchase #2	$35.90	3.471%	$37.1461	$37.15	$37.15	$37.10
Purchase #3	$19.79	5.810%	$20.9398	$20.94	$20.95	$20.90
Purchase #4	$12.47	10.355%	$13.7613	$13.76	$13.75	$13.80
Purchase #5	$119.26	4.321%	$124.4132	$124.41	$124.40	$124.40
Purchase #6	$197.67	9.721%	$216.8855	$216.89	$216.90	$216.90
Purchase #7	$25.65	7.654%	$27.6133	$27.61	$27.60	$27.60
7 purchase totals =	$487.36		$526.6617	$526.66	$526.65	$526.60