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	$94.80	12.739%	$106.8766	$106.88	$106.90	$106.90
Purchase #2	$172.98	3.588%	$179.1865	$179.19	$179.20	$179.20
Purchase #3	$199.78	10.864%	$221.4841	$221.48	$221.50	$221.50
Purchase #4	$132.52	5.505%	$139.8152	$139.82	$139.80	$139.80
Purchase #5	$124.88	4.671%	$130.7131	$130.71	$130.70	$130.70
Purchase #6	$33.34	3.803%	$34.6079	$34.61	$34.60	$34.60
Purchase #7	$109.43	12.533%	$123.1449	$123.14	$123.15	$123.10
7 purchase totals =	$867.73		$935.8283	$935.83	$935.85	$935.80