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	$195.35	5.173%	$205.4555	$205.46	$205.45	$205.50
Purchase #2	$59.39	9.791%	$65.2049	$65.20	$65.20	$65.20
Purchase #3	$43.56	10.371%	$48.0776	$48.08	$48.10	$48.10
Purchase #4	$105.78	11.478%	$117.9214	$117.92	$117.90	$117.90
Purchase #5	$150.83	7.719%	$162.4726	$162.47	$162.45	$162.50
Purchase #6	$69.32	11.341%	$77.1816	$77.18	$77.20	$77.20
Purchase #7	$55.32	7.232%	$59.3207	$59.32	$59.30	$59.30
7 purchase totals =	$679.55		$735.6343	$735.63	$735.60	$735.70