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	$5.71	5.628%	$6.0314	$6.03	$6.05	$6.00
Purchase #2	$162.26	13.427%	$184.0467	$184.05	$184.05	$184.00
Purchase #3	$172.71	4.516%	$180.5096	$180.51	$180.50	$180.50
Purchase #4	$56.25	5.366%	$59.2684	$59.27	$59.25	$59.30
Purchase #5	$122.48	13.529%	$139.0503	$139.05	$139.05	$139.10
Purchase #6	$126.83	12.676%	$142.907	$142.91	$142.90	$142.90
Purchase #7	$221.62	10.301%	$244.4491	$244.45	$244.45	$244.40
7 purchase totals =	$867.86		$956.2625	$956.27	$956.25	$956.20