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	$244.77	10.268%	$269.903	$269.90	$269.90	$269.90
Purchase #2	$35.63	3.274%	$36.7965	$36.80	$36.80	$36.80
Purchase #3	$34.65	9.303%	$37.8735	$37.87	$37.85	$37.90
Purchase #4	$225.83	10.485%	$249.5083	$249.51	$249.50	$249.50
Purchase #5	$113.65	8.253%	$123.0295	$123.03	$123.05	$123.00
Purchase #6	$131.35	10.755%	$145.4767	$145.48	$145.50	$145.50
Purchase #7	$80.79	5.532%	$85.2593	$85.26	$85.25	$85.30
7 purchase totals =	$866.67		$947.8468	$947.85	$947.85	$947.90