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	$214.77	8.667%	$233.3841	$233.38	$233.40	$233.40
Purchase #2	$33.39	6.303%	$35.4946	$35.49	$35.50	$35.50
Purchase #3	$216.62	13.682%	$246.2579	$246.26	$246.25	$246.30
Purchase #4	$56.37	9.484%	$61.7161	$61.72	$61.70	$61.70
Purchase #5	$152.35	10.356%	$168.1274	$168.13	$168.15	$168.10
Purchase #6	$146.81	5.676%	$155.1429	$155.14	$155.15	$155.10
Purchase #7	$176.85	7.344%	$189.8379	$189.84	$189.85	$189.80
7 purchase totals =	$997.16		$1,089.9609	$1,089.96	$1,090.00	$1,089.90