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	$124.43	9.650%	$136.4375	$136.44	$136.45	$136.40
Purchase #2	$172.51	5.268%	$181.5978	$181.60	$181.60	$181.60
Purchase #3	$160.32	7.310%	$172.0394	$172.04	$172.05	$172.00
Purchase #4	$132.98	4.691%	$139.2181	$139.22	$139.20	$139.20
Purchase #5	$212.38	4.867%	$222.7165	$222.72	$222.70	$222.70
Purchase #6	$227.34	8.765%	$247.2664	$247.27	$247.25	$247.30
Purchase #7	$167.67	11.738%	$187.3511	$187.35	$187.35	$187.40
7 purchase totals =	$1,197.63		$1,286.6268	$1,286.64	$1,286.60	$1,286.60