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	$232.75	3.805%	$241.6061	$241.61	$241.60	$241.60
Purchase #2	$140.70	7.627%	$151.4312	$151.43	$151.45	$151.40
Purchase #3	$44.89	7.819%	$48.3999	$48.40	$48.40	$48.40
Purchase #4	$236.45	9.235%	$258.2862	$258.29	$258.30	$258.30
Purchase #5	$166.92	10.447%	$184.3581	$184.36	$184.35	$184.40
Purchase #6	$28.47	12.447%	$32.0137	$32.01	$32.00	$32.00
Purchase #7	$67.50	5.735%	$71.3711	$71.37	$71.35	$71.40
7 purchase totals =	$917.68		$987.4663	$987.47	$987.45	$987.50