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	$231.82	5.388%	$244.3105	$244.31	$244.30	$244.30
Purchase #2	$215.60	9.471%	$236.0195	$236.02	$236.00	$236.00
Purchase #3	$129.66	9.576%	$142.0762	$142.08	$142.10	$142.10
Purchase #4	$135.56	10.850%	$150.2683	$150.27	$150.25	$150.30
Purchase #5	$112.61	13.537%	$127.854	$127.85	$127.85	$127.90
Purchase #6	$183.83	3.180%	$189.6758	$189.68	$189.70	$189.70
Purchase #7	$117.25	12.603%	$132.027	$132.03	$132.05	$132.00
7 purchase totals =	$1,126.33		$1,222.2313	$1,222.24	$1,222.25	$1,222.30