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	$62.79	7.262%	$67.3498	$67.35	$67.35	$67.30
Purchase #2	$113.63	13.274%	$128.7132	$128.71	$128.70	$128.70
Purchase #3	$182.92	3.746%	$189.7722	$189.77	$189.75	$189.80
Purchase #4	$50.57	7.119%	$54.1701	$54.17	$54.15	$54.20
Purchase #5	$28.37	13.283%	$32.1384	$32.14	$32.15	$32.10
Purchase #6	$77.86	4.802%	$81.5988	$81.60	$81.60	$81.60
Purchase #7	$113.48	8.847%	$123.5196	$123.52	$123.50	$123.50
7 purchase totals =	$629.62		$677.2621	$677.26	$677.20	$677.20