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	$114.63	11.473%	$127.7815	$127.78	$127.80	$127.80
Purchase #2	$156.56	10.807%	$173.4794	$173.48	$173.50	$173.50
Purchase #3	$219.29	11.730%	$245.0127	$245.01	$245.00	$245.00
Purchase #4	$35.58	10.836%	$39.4354	$39.44	$39.45	$39.40
Purchase #5	$42.76	4.551%	$44.706	$44.71	$44.70	$44.70
Purchase #6	$10.86	8.642%	$11.7985	$11.80	$11.80	$11.80
Purchase #7	$33.55	12.792%	$37.8417	$37.84	$37.85	$37.80
7 purchase totals =	$613.23		$680.0552	$680.06	$680.10	$680.00