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	$89.66	13.248%	$101.5382	$101.54	$101.55	$101.50
Purchase #2	$110.48	5.445%	$116.4956	$116.50	$116.50	$116.50
Purchase #3	$48.51	13.579%	$55.0972	$55.10	$55.10	$55.10
Purchase #4	$228.75	3.452%	$236.6465	$236.65	$236.65	$236.60
Purchase #5	$97.63	13.741%	$111.0453	$111.05	$111.05	$111.00
Purchase #6	$25.59	8.686%	$27.8127	$27.81	$27.80	$27.80
Purchase #7	$190.44	13.868%	$216.8502	$216.85	$216.85	$216.90
7 purchase totals =	$791.06		$865.4857	$865.50	$865.50	$865.40