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	$240.47	11.585%	$268.3284	$268.33	$268.35	$268.30
Purchase #2	$175.68	8.514%	$190.6374	$190.64	$190.65	$190.60
Purchase #3	$25.39	8.667%	$27.5906	$27.59	$27.60	$27.60
Purchase #4	$38.48	10.354%	$42.4642	$42.46	$42.45	$42.50
Purchase #5	$70.98	12.413%	$79.7907	$79.79	$79.80	$79.80
Purchase #6	$189.79	5.788%	$200.775	$200.78	$200.80	$200.80
Purchase #7	$191.78	8.867%	$208.7851	$208.79	$208.80	$208.80
7 purchase totals =	$932.57		$1,018.3714	$1,018.38	$1,018.45	$1,018.40