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	$225.90	4.665%	$236.4382	$236.44	$236.45	$236.40
Purchase #2	$81.54	4.833%	$85.4808	$85.48	$85.50	$85.50
Purchase #3	$119.65	12.775%	$134.9353	$134.94	$134.95	$134.90
Purchase #4	$41.74	9.634%	$45.7612	$45.76	$45.75	$45.80
Purchase #5	$52.39	13.403%	$59.4118	$59.41	$59.40	$59.40
Purchase #6	$28.75	9.291%	$31.4212	$31.42	$31.40	$31.40
Purchase #7	$203.97	4.463%	$213.0732	$213.07	$213.05	$213.10
7 purchase totals =	$753.94		$806.5217	$806.52	$806.50	$806.50