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	$100.61	8.269%	$108.9294	$108.93	$108.95	$108.90
Purchase #2	$245.48	8.370%	$266.0267	$266.03	$266.05	$266.00
Purchase #3	$196.97	13.786%	$224.1243	$224.12	$224.10	$224.10
Purchase #4	$72.83	7.109%	$78.0075	$78.01	$78.00	$78.00
Purchase #5	$240.82	13.761%	$273.9592	$273.96	$273.95	$274.00
Purchase #6	$119.69	13.837%	$136.2515	$136.25	$136.25	$136.30
Purchase #7	$10.94	9.204%	$11.9469	$11.95	$11.95	$11.90
7 purchase totals =	$987.34		$1,099.2455	$1,099.25	$1,099.25	$1,099.20