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	$241.45	13.786%	$274.7363	$274.74	$274.75	$274.70
Purchase #2	$59.93	4.183%	$62.4369	$62.44	$62.45	$62.40
Purchase #3	$161.42	10.838%	$178.9147	$178.91	$178.90	$178.90
Purchase #4	$185.74	5.841%	$196.5891	$196.59	$196.60	$196.60
Purchase #5	$63.82	11.776%	$71.3354	$71.34	$71.35	$71.30
Purchase #6	$40.42	6.184%	$42.9196	$42.92	$42.90	$42.90
Purchase #7	$152.61	13.560%	$173.3039	$173.30	$173.30	$173.30
7 purchase totals =	$905.39		$1,000.2359	$1,000.24	$1,000.25	$1,000.10