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	$61.40	5.346%	$64.6824	$64.68	$64.70	$64.70
Purchase #2	$32.42	6.511%	$34.5309	$34.53	$34.55	$34.50
Purchase #3	$19.57	9.568%	$21.4425	$21.44	$21.45	$21.40
Purchase #4	$72.43	12.338%	$81.3664	$81.37	$81.35	$81.40
Purchase #5	$190.45	4.480%	$198.9822	$198.98	$199.00	$199.00
Purchase #6	$77.98	5.769%	$82.4787	$82.48	$82.50	$82.50
Purchase #7	$83.68	8.176%	$90.5217	$90.52	$90.50	$90.50
7 purchase totals =	$537.93		$574.0048	$574.00	$574.05	$574.00