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	$74.96	11.742%	$83.7618	$83.76	$83.75	$83.80
Purchase #2	$11.94	13.845%	$13.5931	$13.59	$13.60	$13.60
Purchase #3	$132.83	10.415%	$146.6642	$146.66	$146.65	$146.70
Purchase #4	$102.35	12.257%	$114.895	$114.90	$114.90	$114.90
Purchase #5	$127.82	8.599%	$138.8112	$138.81	$138.80	$138.80
Purchase #6	$189.89	10.673%	$210.157	$210.16	$210.15	$210.20
Purchase #7	$114.56	3.515%	$118.5868	$118.59	$118.60	$118.60
7 purchase totals =	$754.35		$826.4691	$826.47	$826.45	$826.60