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	$139.72	4.595%	$146.1401	$146.14	$146.15	$146.10
Purchase #2	$206.47	7.501%	$221.9573	$221.96	$221.95	$222.00
Purchase #3	$90.55	11.483%	$100.9479	$100.95	$100.95	$100.90
Purchase #4	$51.25	4.472%	$53.5419	$53.54	$53.55	$53.50
Purchase #5	$69.87	4.249%	$72.8388	$72.84	$72.85	$72.80
Purchase #6	$94.55	10.274%	$104.2641	$104.26	$104.25	$104.30
Purchase #7	$175.93	11.376%	$195.9438	$195.94	$195.95	$195.90
7 purchase totals =	$828.34		$895.6339	$895.63	$895.65	$895.50