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	$83.37	7.398%	$89.5377	$89.54	$89.55	$89.50
Purchase #2	$197.94	12.789%	$223.2545	$223.25	$223.25	$223.30
Purchase #3	$188.79	13.138%	$213.5932	$213.59	$213.60	$213.60
Purchase #4	$61.47	7.774%	$66.2487	$66.25	$66.25	$66.20
Purchase #5	$164.37	11.234%	$182.8353	$182.84	$182.85	$182.80
Purchase #6	$49.45	3.546%	$51.2035	$51.20	$51.20	$51.20
Purchase #7	$186.68	12.134%	$209.3318	$209.33	$209.35	$209.30
7 purchase totals =	$932.07		$1,036.0047	$1,036.00	$1,036.05	$1,035.90