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	$149.48	4.350%	$155.9824	$155.98	$156.00	$156.00
Purchase #2	$169.40	12.257%	$190.1634	$190.16	$190.15	$190.20
Purchase #3	$89.46	9.387%	$97.8576	$97.86	$97.85	$97.90
Purchase #4	$197.97	9.393%	$216.5653	$216.57	$216.55	$216.60
Purchase #5	$33.51	4.108%	$34.8866	$34.89	$34.90	$34.90
Purchase #6	$101.42	7.778%	$109.3084	$109.31	$109.30	$109.30
Purchase #7	$59.48	5.439%	$62.7151	$62.72	$62.70	$62.70
7 purchase totals =	$800.72		$867.4788	$867.49	$867.45	$867.60