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	$112.46	12.511%	$126.5299	$126.53	$126.55	$126.50
Purchase #2	$214.65	3.650%	$222.4847	$222.48	$222.50	$222.50
Purchase #3	$238.55	8.274%	$258.2876	$258.29	$258.30	$258.30
Purchase #4	$78.30	12.239%	$87.8831	$87.88	$87.90	$87.90
Purchase #5	$128.73	13.420%	$146.0056	$146.01	$146.00	$146.00
Purchase #6	$53.47	7.105%	$57.269	$57.27	$57.25	$57.30
Purchase #7	$250.79	7.193%	$268.8293	$268.83	$268.85	$268.80
7 purchase totals =	$1,076.95		$1,167.2892	$1,167.29	$1,167.35	$1,167.30