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	$90.48	5.671%	$95.6111	$95.61	$95.60	$95.60
Purchase #2	$229.72	4.662%	$240.4295	$240.43	$240.45	$240.40
Purchase #3	$25.73	8.686%	$27.9649	$27.96	$27.95	$28.00
Purchase #4	$6.52	13.802%	$7.4199	$7.42	$7.40	$7.40
Purchase #5	$38.51	12.219%	$43.2155	$43.22	$43.20	$43.20
Purchase #6	$48.50	6.836%	$51.8155	$51.82	$51.80	$51.80
Purchase #7	$192.45	12.533%	$216.5698	$216.57	$216.55	$216.60
7 purchase totals =	$631.91		$683.0262	$683.03	$682.95	$683.00