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	$78.94	11.432%	$87.9644	$87.96	$87.95	$88.00
Purchase #2	$12.38	6.384%	$13.1703	$13.17	$13.15	$13.20
Purchase #3	$199.50	13.814%	$227.0589	$227.06	$227.05	$227.10
Purchase #4	$80.78	11.119%	$89.7619	$89.76	$89.75	$89.80
Purchase #5	$55.62	13.208%	$62.9663	$62.97	$62.95	$63.00
Purchase #6	$44.34	3.405%	$45.8498	$45.85	$45.85	$45.80
Purchase #7	$137.29	5.367%	$144.6584	$144.66	$144.65	$144.70
7 purchase totals =	$608.85		$671.4300	$671.43	$671.35	$671.60