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	$88.39	11.330%	$98.4046	$98.40	$98.40	$98.40
Purchase #2	$26.71	6.792%	$28.5241	$28.52	$28.50	$28.50
Purchase #3	$174.96	12.368%	$196.5991	$196.60	$196.60	$196.60
Purchase #4	$228.48	11.862%	$255.5823	$255.58	$255.60	$255.60
Purchase #5	$143.45	7.565%	$154.302	$154.30	$154.30	$154.30
Purchase #6	$222.26	9.365%	$243.0746	$243.07	$243.05	$243.10
Purchase #7	$75.98	9.545%	$83.2323	$83.23	$83.25	$83.20
7 purchase totals =	$960.23		$1,059.7190	$1,059.70	$1,059.70	$1,059.70