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	$238.59	11.248%	$265.4266	$265.43	$265.45	$265.40
Purchase #2	$244.44	4.515%	$255.4765	$255.48	$255.50	$255.50
Purchase #3	$180.67	5.483%	$190.5761	$190.58	$190.60	$190.60
Purchase #4	$228.85	11.112%	$254.2798	$254.28	$254.30	$254.30
Purchase #5	$54.63	8.696%	$59.3806	$59.38	$59.40	$59.40
Purchase #6	$110.33	11.103%	$122.5799	$122.58	$122.60	$122.60
Purchase #7	$63.49	7.451%	$68.2206	$68.22	$68.20	$68.20
7 purchase totals =	$1,121.00		$1,215.9401	$1,215.95	$1,216.05	$1,216.00