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	$47.94	10.635%	$53.0384	$53.04	$53.05	$53.00
Purchase #2	$23.79	8.819%	$25.888	$25.89	$25.90	$25.90
Purchase #3	$132.83	6.762%	$141.812	$141.81	$141.80	$141.80
Purchase #4	$38.93	10.236%	$42.9149	$42.91	$42.90	$42.90
Purchase #5	$32.78	12.163%	$36.767	$36.77	$36.75	$36.80
Purchase #6	$133.33	13.609%	$151.4749	$151.47	$151.45	$151.50
Purchase #7	$193.92	13.708%	$220.5026	$220.50	$220.50	$220.50
7 purchase totals =	$603.52		$672.3978	$672.39	$672.35	$672.40