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	$217.96	13.273%	$246.8898	$246.89	$246.90	$246.90
Purchase #2	$38.30	7.458%	$41.1564	$41.16	$41.15	$41.20
Purchase #3	$7.51	5.173%	$7.8985	$7.90	$7.90	$7.90
Purchase #4	$30.93	13.436%	$35.0858	$35.09	$35.10	$35.10
Purchase #5	$54.83	8.759%	$59.6326	$59.63	$59.65	$59.60
Purchase #6	$61.33	3.321%	$63.3668	$63.37	$63.35	$63.40
Purchase #7	$150.73	3.504%	$156.0116	$156.01	$156.00	$156.00
7 purchase totals =	$561.59		$610.0415	$610.05	$610.05	$610.10