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	$200.55	8.172%	$216.9389	$216.94	$216.95	$216.90
Purchase #2	$57.27	4.725%	$59.976	$59.98	$60.00	$60.00
Purchase #3	$57.56	8.421%	$62.4071	$62.41	$62.40	$62.40
Purchase #4	$40.90	10.579%	$45.2268	$45.23	$45.25	$45.20
Purchase #5	$226.65	4.526%	$236.9082	$236.91	$236.90	$236.90
Purchase #6	$35.25	12.341%	$39.6002	$39.60	$39.60	$39.60
Purchase #7	$249.44	11.645%	$278.4873	$278.49	$278.50	$278.50
7 purchase totals =	$867.62		$939.5445	$939.56	$939.60	$939.50