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	$203.85	9.142%	$222.486	$222.49	$222.50	$222.50
Purchase #2	$178.86	4.236%	$186.4365	$186.44	$186.45	$186.40
Purchase #3	$243.43	12.307%	$273.3889	$273.39	$273.40	$273.40
Purchase #4	$246.39	6.187%	$261.6341	$261.63	$261.65	$261.60
Purchase #5	$72.78	10.521%	$80.4372	$80.44	$80.45	$80.40
Purchase #6	$31.61	8.146%	$34.185	$34.19	$34.20	$34.20
Purchase #7	$61.32	6.463%	$65.2831	$65.28	$65.30	$65.30
7 purchase totals =	$1,038.24		$1,123.8508	$1,123.86	$1,123.95	$1,123.80