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	$50.75	8.158%	$54.8902	$54.89	$54.90	$54.90
Purchase #2	$130.32	5.682%	$137.7248	$137.72	$137.70	$137.70
Purchase #3	$197.56	6.618%	$210.6345	$210.63	$210.65	$210.60
Purchase #4	$231.26	13.224%	$261.8418	$261.84	$261.85	$261.80
Purchase #5	$148.26	5.477%	$156.3802	$156.38	$156.40	$156.40
Purchase #6	$30.62	12.321%	$34.3927	$34.39	$34.40	$34.40
Purchase #7	$132.83	11.840%	$148.5571	$148.56	$148.55	$148.60
7 purchase totals =	$921.60		$1,004.4213	$1,004.41	$1,004.45	$1,004.40