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	$215.56	3.168%	$222.3889	$222.39	$222.40	$222.40
Purchase #2	$197.86	3.362%	$204.5121	$204.51	$204.50	$204.50
Purchase #3	$127.78	7.426%	$137.2689	$137.27	$137.25	$137.30
Purchase #4	$148.85	5.752%	$157.4119	$157.41	$157.40	$157.40
Purchase #5	$116.92	8.678%	$127.0663	$127.07	$127.05	$127.10
Purchase #6	$96.26	6.577%	$102.591	$102.59	$102.60	$102.60
Purchase #7	$243.83	12.739%	$274.8915	$274.89	$274.90	$274.90
7 purchase totals =	$1,147.06		$1,226.1306	$1,226.13	$1,226.10	$1,226.20