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	$53.95	3.287%	$55.7233	$55.72	$55.70	$55.70
Purchase #2	$7.90	7.457%	$8.4891	$8.49	$8.50	$8.50
Purchase #3	$38.54	10.467%	$42.574	$42.57	$42.55	$42.60
Purchase #4	$203.42	10.356%	$224.4862	$224.49	$224.50	$224.50
Purchase #5	$209.96	11.186%	$233.4461	$233.45	$233.45	$233.40
Purchase #6	$119.54	13.812%	$136.0509	$136.05	$136.05	$136.10
Purchase #7	$10.37	13.630%	$11.7834	$11.78	$11.80	$11.80
7 purchase totals =	$643.68		$712.5530	$712.55	$712.55	$712.60