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	$11.67	7.208%	$12.5112	$12.51	$12.50	$12.50
Purchase #2	$12.96	13.788%	$14.7469	$14.75	$14.75	$14.70
Purchase #3	$60.57	11.590%	$67.5901	$67.59	$67.60	$67.60
Purchase #4	$68.94	5.114%	$72.4656	$72.47	$72.45	$72.50
Purchase #5	$165.43	11.537%	$184.5157	$184.52	$184.50	$184.50
Purchase #6	$63.90	10.703%	$70.7392	$70.74	$70.75	$70.70
Purchase #7	$55.44	10.564%	$61.2967	$61.30	$61.30	$61.30
7 purchase totals =	$438.91		$483.8654	$483.88	$483.85	$483.80