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	$79.48	5.115%	$83.5454	$83.55	$83.55	$83.50
Purchase #2	$27.89	10.256%	$30.7504	$30.75	$30.75	$30.80
Purchase #3	$196.42	10.148%	$216.3527	$216.35	$216.35	$216.40
Purchase #4	$36.33	11.757%	$40.6013	$40.60	$40.60	$40.60
Purchase #5	$83.92	10.181%	$92.4639	$92.46	$92.45	$92.50
Purchase #6	$111.53	4.540%	$116.5935	$116.59	$116.60	$116.60
Purchase #7	$116.37	7.204%	$124.7533	$124.75	$124.75	$124.80
7 purchase totals =	$651.94		$705.0605	$705.05	$705.05	$705.20