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	$192.78	9.291%	$210.6912	$210.69	$210.70	$210.70
Purchase #2	$172.44	8.656%	$187.3664	$187.37	$187.35	$187.40
Purchase #3	$71.32	6.471%	$75.9351	$75.94	$75.95	$75.90
Purchase #4	$31.61	3.721%	$32.7862	$32.79	$32.80	$32.80
Purchase #5	$219.89	3.308%	$227.164	$227.16	$227.15	$227.20
Purchase #6	$187.63	6.311%	$199.4713	$199.47	$199.45	$199.50
Purchase #7	$75.40	10.697%	$83.4655	$83.47	$83.45	$83.50
7 purchase totals =	$951.07		$1,016.8797	$1,016.89	$1,016.85	$1,017.00