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	$32.83	4.674%	$34.3645	$34.36	$34.35	$34.40
Purchase #2	$40.71	6.767%	$43.4648	$43.46	$43.45	$43.50
Purchase #3	$167.32	13.617%	$190.104	$190.10	$190.10	$190.10
Purchase #4	$131.29	5.132%	$138.0278	$138.03	$138.05	$138.00
Purchase #5	$5.42	7.628%	$5.8334	$5.83	$5.85	$5.80
Purchase #6	$99.96	10.424%	$110.3798	$110.38	$110.40	$110.40
Purchase #7	$207.25	7.119%	$222.0041	$222.00	$222.00	$222.00
7 purchase totals =	$684.78		$744.1784	$744.16	$744.20	$744.20