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	$113.45	9.168%	$123.8511	$123.85	$123.85	$123.90
Purchase #2	$49.39	9.416%	$54.0406	$54.04	$54.05	$54.00
Purchase #3	$38.48	3.730%	$39.9153	$39.92	$39.90	$39.90
Purchase #4	$37.44	9.701%	$41.0721	$41.07	$41.05	$41.10
Purchase #5	$244.89	11.521%	$273.1038	$273.10	$273.10	$273.10
Purchase #6	$65.44	12.655%	$73.7214	$73.72	$73.70	$73.70
Purchase #7	$68.36	6.680%	$72.9264	$72.93	$72.95	$72.90
7 purchase totals =	$617.45		$678.6307	$678.63	$678.60	$678.60