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	$156.44	10.233%	$172.4485	$172.45	$172.45	$172.40
Purchase #2	$31.61	9.242%	$34.5314	$34.53	$34.55	$34.50
Purchase #3	$195.71	7.389%	$210.171	$210.17	$210.15	$210.20
Purchase #4	$205.87	7.786%	$221.899	$221.90	$221.90	$221.90
Purchase #5	$30.63	7.650%	$32.9732	$32.97	$32.95	$33.00
Purchase #6	$97.51	12.189%	$109.3955	$109.40	$109.40	$109.40
Purchase #7	$62.92	11.246%	$69.996	$70.00	$70.00	$70.00
7 purchase totals =	$780.69		$851.4146	$851.42	$851.40	$851.40