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	$134.98	11.806%	$150.9157	$150.92	$150.90	$150.90
Purchase #2	$237.87	3.203%	$245.489	$245.49	$245.50	$245.50
Purchase #3	$231.36	5.624%	$244.3717	$244.37	$244.35	$244.40
Purchase #4	$54.58	9.653%	$59.8486	$59.85	$59.85	$59.80
Purchase #5	$23.43	12.615%	$26.3857	$26.39	$26.40	$26.40
Purchase #6	$165.58	8.742%	$180.055	$180.06	$180.05	$180.10
Purchase #7	$54.83	9.214%	$59.882	$59.88	$59.90	$59.90
7 purchase totals =	$902.63		$966.9477	$966.96	$966.95	$967.00