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	$53.30	8.483%	$57.8214	$57.82	$57.80	$57.80
Purchase #2	$102.31	5.136%	$107.5646	$107.56	$107.55	$107.60
Purchase #3	$246.99	12.624%	$278.17	$278.17	$278.15	$278.20
Purchase #4	$66.28	11.430%	$73.8558	$73.86	$73.85	$73.90
Purchase #5	$42.54	9.812%	$46.714	$46.71	$46.70	$46.70
Purchase #6	$91.27	3.632%	$94.5849	$94.58	$94.60	$94.60
Purchase #7	$78.77	6.499%	$83.8893	$83.89	$83.90	$83.90
7 purchase totals =	$681.46		$742.6000	$742.59	$742.55	$742.70