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	$128.55	11.440%	$143.2561	$143.26	$143.25	$143.30
Purchase #2	$185.51	10.310%	$204.6361	$204.64	$204.65	$204.60
Purchase #3	$38.50	3.463%	$39.8333	$39.83	$39.85	$39.80
Purchase #4	$132.37	10.691%	$146.5217	$146.52	$146.50	$146.50
Purchase #5	$56.57	4.829%	$59.3018	$59.30	$59.30	$59.30
Purchase #6	$100.53	12.144%	$112.7384	$112.74	$112.75	$112.70
Purchase #7	$7.98	11.788%	$8.9207	$8.92	$8.90	$8.90
7 purchase totals =	$650.01		$715.2081	$715.21	$715.20	$715.10