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	$236.88	9.775%	$260.035	$260.04	$260.05	$260.00
Purchase #2	$114.96	11.215%	$127.8528	$127.85	$127.85	$127.90
Purchase #3	$164.52	13.266%	$186.3452	$186.35	$186.35	$186.30
Purchase #4	$81.73	10.847%	$90.5953	$90.60	$90.60	$90.60
Purchase #5	$170.49	6.666%	$181.8549	$181.85	$181.85	$181.90
Purchase #6	$146.80	6.743%	$156.6987	$156.70	$156.70	$156.70
Purchase #7	$68.48	7.468%	$73.5941	$73.59	$73.60	$73.60
7 purchase totals =	$983.86		$1,076.9760	$1,076.98	$1,077.00	$1,077.00