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	$46.94	3.526%	$48.5951	$48.60	$48.60	$48.60
Purchase #2	$81.51	13.462%	$92.4829	$92.48	$92.50	$92.50
Purchase #3	$212.97	4.867%	$223.3352	$223.34	$223.35	$223.30
Purchase #4	$131.33	6.820%	$140.2867	$140.29	$140.30	$140.30
Purchase #5	$250.86	10.807%	$277.9704	$277.97	$277.95	$278.00
Purchase #6	$16.72	12.790%	$18.8585	$18.86	$18.85	$18.90
Purchase #7	$59.69	10.672%	$66.0601	$66.06	$66.05	$66.10
7 purchase totals =	$800.02		$867.5889	$867.60	$867.60	$867.70