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	$240.32	5.508%	$253.5568	$253.56	$253.55	$253.60
Purchase #2	$214.76	8.873%	$233.8157	$233.82	$233.80	$233.80
Purchase #3	$81.53	11.439%	$90.8562	$90.86	$90.85	$90.90
Purchase #4	$240.96	10.313%	$265.8102	$265.81	$265.80	$265.80
Purchase #5	$76.45	8.384%	$82.8596	$82.86	$82.85	$82.90
Purchase #6	$55.53	13.526%	$63.041	$63.04	$63.05	$63.00
Purchase #7	$156.30	11.673%	$174.5449	$174.54	$174.55	$174.50
7 purchase totals =	$1,065.85		$1,164.4844	$1,164.49	$1,164.45	$1,164.50