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	$51.34	13.807%	$58.4285	$58.43	$58.45	$58.40
Purchase #2	$201.74	7.480%	$216.8302	$216.83	$216.85	$216.80
Purchase #3	$215.30	12.224%	$241.6183	$241.62	$241.60	$241.60
Purchase #4	$41.50	3.182%	$42.8205	$42.82	$42.80	$42.80
Purchase #5	$134.55	13.651%	$152.9174	$152.92	$152.90	$152.90
Purchase #6	$142.55	11.230%	$158.5584	$158.56	$158.55	$158.60
Purchase #7	$105.55	6.647%	$112.5659	$112.57	$112.55	$112.60
7 purchase totals =	$892.53		$983.7392	$983.75	$983.70	$983.70