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	$184.70	13.653%	$209.9171	$209.92	$209.90	$209.90
Purchase #2	$108.56	3.842%	$112.7309	$112.73	$112.75	$112.70
Purchase #3	$15.37	3.389%	$15.8909	$15.89	$15.90	$15.90
Purchase #4	$110.66	11.682%	$123.5873	$123.59	$123.60	$123.60
Purchase #5	$113.34	13.277%	$128.3882	$128.39	$128.40	$128.40
Purchase #6	$220.83	7.309%	$236.9705	$236.97	$236.95	$237.00
Purchase #7	$43.64	9.739%	$47.8901	$47.89	$47.90	$47.90
7 purchase totals =	$797.10		$875.3750	$875.38	$875.40	$875.40