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	$209.45	7.851%	$225.8939	$225.89	$225.90	$225.90
Purchase #2	$60.35	6.215%	$64.1008	$64.10	$64.10	$64.10
Purchase #3	$108.96	4.246%	$113.5864	$113.59	$113.60	$113.60
Purchase #4	$41.67	8.639%	$45.2699	$45.27	$45.25	$45.30
Purchase #5	$88.29	12.239%	$99.0958	$99.10	$99.10	$99.10
Purchase #6	$171.34	12.290%	$192.3977	$192.40	$192.40	$192.40
Purchase #7	$193.47	8.326%	$209.5783	$209.58	$209.60	$209.60
7 purchase totals =	$873.53		$949.9228	$949.93	$949.95	$950.00