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	$150.54	3.868%	$156.3629	$156.36	$156.35	$156.40
Purchase #2	$99.89	10.733%	$110.6112	$110.61	$110.60	$110.60
Purchase #3	$137.45	12.687%	$154.8883	$154.89	$154.90	$154.90
Purchase #4	$62.77	3.744%	$65.1201	$65.12	$65.10	$65.10
Purchase #5	$110.62	6.391%	$117.6897	$117.69	$117.70	$117.70
Purchase #6	$82.98	8.873%	$90.3428	$90.34	$90.35	$90.30
Purchase #7	$117.46	13.227%	$132.9964	$133.00	$133.00	$133.00
7 purchase totals =	$761.71		$828.0114	$828.01	$828.00	$828.00