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	$82.36	5.152%	$86.6032	$86.60	$86.60	$86.60
Purchase #2	$32.27	8.307%	$34.9507	$34.95	$34.95	$35.00
Purchase #3	$63.77	13.434%	$72.3369	$72.34	$72.35	$72.30
Purchase #4	$127.26	13.340%	$144.2365	$144.24	$144.25	$144.20
Purchase #5	$134.52	6.670%	$143.4925	$143.49	$143.50	$143.50
Purchase #6	$184.66	7.512%	$198.5317	$198.53	$198.55	$198.50
Purchase #7	$68.52	7.659%	$73.7679	$73.77	$73.75	$73.80
7 purchase totals =	$693.36		$753.9194	$753.92	$753.95	$753.90