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	$102.38	4.445%	$106.9308	$106.93	$106.95	$106.90
Purchase #2	$45.35	5.850%	$48.003	$48.00	$48.00	$48.00
Purchase #3	$53.48	7.703%	$57.5996	$57.60	$57.60	$57.60
Purchase #4	$6.72	9.104%	$7.3318	$7.33	$7.35	$7.30
Purchase #5	$52.58	13.210%	$59.5258	$59.53	$59.55	$59.50
Purchase #6	$11.25	11.804%	$12.578	$12.58	$12.60	$12.60
Purchase #7	$216.48	3.107%	$223.206	$223.21	$223.20	$223.20
7 purchase totals =	$488.24		$515.1750	$515.18	$515.25	$515.10