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	$34.43	3.717%	$35.7098	$35.71	$35.70	$35.70
Purchase #2	$89.33	12.143%	$100.1773	$100.18	$100.20	$100.20
Purchase #3	$57.96	6.129%	$61.5124	$61.51	$61.50	$61.50
Purchase #4	$234.84	6.268%	$249.5598	$249.56	$249.55	$249.60
Purchase #5	$114.80	7.439%	$123.34	$123.34	$123.35	$123.30
Purchase #6	$209.29	5.612%	$221.0354	$221.04	$221.05	$221.00
Purchase #7	$186.51	10.587%	$206.2558	$206.26	$206.25	$206.30
7 purchase totals =	$927.16		$997.5905	$997.60	$997.60	$997.60