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	$222.96	6.759%	$238.0299	$238.03	$238.05	$238.00
Purchase #2	$215.40	3.214%	$222.323	$222.32	$222.30	$222.30
Purchase #3	$189.91	11.426%	$211.6091	$211.61	$211.60	$211.60
Purchase #4	$63.57	3.300%	$65.6678	$65.67	$65.65	$65.70
Purchase #5	$9.67	5.273%	$10.1799	$10.18	$10.20	$10.20
Purchase #6	$164.44	5.740%	$173.8789	$173.88	$173.90	$173.90
Purchase #7	$47.49	9.222%	$51.8695	$51.87	$51.85	$51.90
7 purchase totals =	$913.44		$973.5581	$973.56	$973.55	$973.60