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	$217.55	5.511%	$229.5392	$229.54	$229.55	$229.50
Purchase #2	$65.52	9.853%	$71.9757	$71.98	$72.00	$72.00
Purchase #3	$32.84	5.447%	$34.6288	$34.63	$34.65	$34.60
Purchase #4	$144.88	13.567%	$164.5359	$164.54	$164.55	$164.50
Purchase #5	$61.44	4.179%	$64.0076	$64.01	$64.00	$64.00
Purchase #6	$98.90	4.446%	$103.2971	$103.30	$103.30	$103.30
Purchase #7	$40.73	12.584%	$45.8555	$45.86	$45.85	$45.90
7 purchase totals =	$661.86		$713.8398	$713.86	$713.90	$713.80