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	$246.27	7.108%	$263.7749	$263.77	$263.75	$263.80
Purchase #2	$128.79	10.151%	$141.8635	$141.86	$141.85	$141.90
Purchase #3	$82.96	3.197%	$85.6122	$85.61	$85.60	$85.60
Purchase #4	$246.81	12.212%	$276.9504	$276.95	$276.95	$277.00
Purchase #5	$103.43	4.737%	$108.3295	$108.33	$108.35	$108.30
Purchase #6	$187.48	4.691%	$196.2747	$196.27	$196.25	$196.30
Purchase #7	$26.50	10.531%	$29.2907	$29.29	$29.30	$29.30
7 purchase totals =	$1,022.24		$1,102.0959	$1,102.08	$1,102.05	$1,102.20