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	$137.96	7.338%	$148.0835	$148.08	$148.10	$148.10
Purchase #2	$186.83	7.441%	$200.732	$200.73	$200.75	$200.70
Purchase #3	$115.42	11.421%	$128.6021	$128.60	$128.60	$128.60
Purchase #4	$150.43	6.678%	$160.4757	$160.48	$160.50	$160.50
Purchase #5	$133.83	12.788%	$150.9442	$150.94	$150.95	$150.90
Purchase #6	$61.47	7.176%	$65.8811	$65.88	$65.90	$65.90
Purchase #7	$181.93	10.558%	$201.1382	$201.14	$201.15	$201.10
7 purchase totals =	$967.87		$1,055.8568	$1,055.85	$1,055.95	$1,055.80