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	$40.52	5.787%	$42.8649	$42.86	$42.85	$42.90
Purchase #2	$174.89	7.522%	$188.0452	$188.05	$188.05	$188.00
Purchase #3	$222.38	10.796%	$246.3881	$246.39	$246.40	$246.40
Purchase #4	$9.92	9.136%	$10.8263	$10.83	$10.85	$10.80
Purchase #5	$141.57	6.103%	$150.21	$150.21	$150.20	$150.20
Purchase #6	$91.90	10.365%	$101.4254	$101.43	$101.45	$101.40
Purchase #7	$77.75	10.119%	$85.6175	$85.62	$85.60	$85.60
7 purchase totals =	$758.93		$825.3774	$825.39	$825.40	$825.30