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	$153.63	10.407%	$169.6183	$169.62	$169.60	$169.60
Purchase #2	$162.68	5.145%	$171.0499	$171.05	$171.05	$171.00
Purchase #3	$64.61	11.152%	$71.8153	$71.82	$71.80	$71.80
Purchase #4	$161.34	11.705%	$180.2248	$180.22	$180.20	$180.20
Purchase #5	$122.48	13.568%	$139.0981	$139.10	$139.10	$139.10
Purchase #6	$59.78	11.200%	$66.4754	$66.48	$66.50	$66.50
Purchase #7	$6.72	11.547%	$7.496	$7.50	$7.50	$7.50
7 purchase totals =	$731.24		$805.7778	$805.79	$805.75	$805.70