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	$222.84	11.749%	$249.0215	$249.02	$249.00	$249.00
Purchase #2	$245.74	11.275%	$273.4472	$273.45	$273.45	$273.40
Purchase #3	$141.66	10.144%	$156.03	$156.03	$156.05	$156.00
Purchase #4	$31.57	4.252%	$32.9124	$32.91	$32.90	$32.90
Purchase #5	$140.82	13.276%	$159.5153	$159.52	$159.50	$159.50
Purchase #6	$20.92	4.665%	$21.8959	$21.90	$21.90	$21.90
Purchase #7	$189.68	6.811%	$202.5991	$202.60	$202.60	$202.60
7 purchase totals =	$993.23		$1,095.4214	$1,095.43	$1,095.40	$1,095.30