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	$107.34	8.416%	$116.3737	$116.37	$116.35	$116.40
Purchase #2	$200.72	13.339%	$227.494	$227.49	$227.50	$227.50
Purchase #3	$211.55	5.832%	$223.8876	$223.89	$223.90	$223.90
Purchase #4	$171.53	11.115%	$190.5956	$190.60	$190.60	$190.60
Purchase #5	$141.43	6.496%	$150.6173	$150.62	$150.60	$150.60
Purchase #6	$148.99	11.555%	$166.2058	$166.21	$166.20	$166.20
Purchase #7	$207.34	5.429%	$218.5965	$218.60	$218.60	$218.60
7 purchase totals =	$1,188.90		$1,293.7705	$1,293.78	$1,293.75	$1,293.80