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	$141.95	13.834%	$161.5874	$161.59	$161.60	$161.60
Purchase #2	$109.57	9.149%	$119.5946	$119.59	$119.60	$119.60
Purchase #3	$200.41	8.864%	$218.1743	$218.17	$218.15	$218.20
Purchase #4	$216.32	5.674%	$228.594	$228.59	$228.60	$228.60
Purchase #5	$234.58	8.803%	$255.2301	$255.23	$255.25	$255.20
Purchase #6	$219.52	8.655%	$238.5195	$238.52	$238.50	$238.50
Purchase #7	$232.96	13.386%	$264.144	$264.14	$264.15	$264.10
7 purchase totals =	$1,355.31		$1,485.8439	$1,485.83	$1,485.85	$1,485.80