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	$29.83	13.444%	$33.8403	$33.84	$33.85	$33.80
Purchase #2	$11.59	7.319%	$12.4383	$12.44	$12.45	$12.40
Purchase #3	$11.35	9.810%	$12.4634	$12.46	$12.45	$12.50
Purchase #4	$147.64	5.514%	$155.7809	$155.78	$155.80	$155.80
Purchase #5	$61.55	9.706%	$67.524	$67.52	$67.50	$67.50
Purchase #6	$59.82	6.279%	$63.5761	$63.58	$63.60	$63.60
Purchase #7	$112.28	12.187%	$125.9636	$125.96	$125.95	$126.00
7 purchase totals =	$434.06		$471.5866	$471.58	$471.60	$471.60