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	$63.61	12.434%	$71.5193	$71.52	$71.50	$71.50
Purchase #2	$200.66	4.189%	$209.0656	$209.07	$209.05	$209.10
Purchase #3	$82.95	3.124%	$85.5414	$85.54	$85.55	$85.50
Purchase #4	$14.65	7.722%	$15.7813	$15.78	$15.80	$15.80
Purchase #5	$57.82	3.642%	$59.9258	$59.93	$59.95	$59.90
Purchase #6	$157.69	9.526%	$172.7115	$172.71	$172.70	$172.70
Purchase #7	$94.57	3.736%	$98.1031	$98.10	$98.10	$98.10
7 purchase totals =	$671.95		$712.6480	$712.65	$712.65	$712.60