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	$108.68	9.680%	$119.2002	$119.20	$119.20	$119.20
Purchase #2	$216.58	3.373%	$223.8852	$223.89	$223.90	$223.90
Purchase #3	$90.71	10.305%	$100.0577	$100.06	$100.05	$100.10
Purchase #4	$31.77	8.800%	$34.5658	$34.57	$34.55	$34.60
Purchase #5	$245.71	4.613%	$257.0446	$257.04	$257.05	$257.00
Purchase #6	$202.90	11.291%	$225.8094	$225.81	$225.80	$225.80
Purchase #7	$39.43	6.514%	$41.9985	$42.00	$42.00	$42.00
7 purchase totals =	$935.78		$1,002.5614	$1,002.57	$1,002.55	$1,002.60