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	$60.62	8.835%	$65.9758	$65.98	$66.00	$66.00
Purchase #2	$198.50	3.786%	$206.0152	$206.02	$206.00	$206.00
Purchase #3	$156.93	11.788%	$175.4289	$175.43	$175.45	$175.40
Purchase #4	$175.89	8.744%	$191.2698	$191.27	$191.25	$191.30
Purchase #5	$171.44	6.141%	$181.9681	$181.97	$181.95	$182.00
Purchase #6	$104.61	7.651%	$112.6137	$112.61	$112.60	$112.60
Purchase #7	$117.48	9.408%	$128.5325	$128.53	$128.55	$128.50
7 purchase totals =	$985.47		$1,061.8040	$1,061.81	$1,061.80	$1,061.80