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	$111.33	5.524%	$117.4799	$117.48	$117.50	$117.50
Purchase #2	$128.77	11.535%	$143.6236	$143.62	$143.60	$143.60
Purchase #3	$177.45	12.507%	$199.6437	$199.64	$199.65	$199.60
Purchase #4	$208.32	9.706%	$228.5395	$228.54	$228.55	$228.50
Purchase #5	$44.91	9.148%	$49.0184	$49.02	$49.00	$49.00
Purchase #6	$103.86	9.433%	$113.6571	$113.66	$113.65	$113.70
Purchase #7	$168.29	10.223%	$185.4943	$185.49	$185.50	$185.50
7 purchase totals =	$942.93		$1,037.4565	$1,037.45	$1,037.45	$1,037.40