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	$139.94	13.662%	$159.0586	$159.06	$159.05	$159.10
Purchase #2	$95.60	10.281%	$105.4286	$105.43	$105.45	$105.40
Purchase #3	$134.58	7.850%	$145.1445	$145.14	$145.15	$145.10
Purchase #4	$197.62	11.838%	$221.0143	$221.01	$221.00	$221.00
Purchase #5	$179.79	9.233%	$196.39	$196.39	$196.40	$196.40
Purchase #6	$113.83	10.310%	$125.5659	$125.57	$125.55	$125.60
Purchase #7	$13.57	7.205%	$14.5477	$14.55	$14.55	$14.50
7 purchase totals =	$874.93		$967.1496	$967.15	$967.15	$967.10