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	$61.97	5.666%	$65.4812	$65.48	$65.50	$65.50
Purchase #2	$10.72	5.754%	$11.3368	$11.34	$11.35	$11.30
Purchase #3	$186.61	11.776%	$208.5852	$208.59	$208.60	$208.60
Purchase #4	$43.75	11.686%	$48.8626	$48.86	$48.85	$48.90
Purchase #5	$161.64	5.458%	$170.4623	$170.46	$170.45	$170.50
Purchase #6	$105.38	13.801%	$119.9235	$119.92	$119.90	$119.90
Purchase #7	$218.37	3.140%	$225.2268	$225.23	$225.25	$225.20
7 purchase totals =	$788.44		$849.8784	$849.88	$849.90	$849.90