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	$219.57	4.563%	$229.589	$229.59	$229.60	$229.60
Purchase #2	$103.39	8.789%	$112.4769	$112.48	$112.50	$112.50
Purchase #3	$215.80	7.143%	$231.2146	$231.21	$231.20	$231.20
Purchase #4	$28.97	7.233%	$31.0654	$31.07	$31.05	$31.10
Purchase #5	$247.53	13.504%	$280.9565	$280.96	$280.95	$281.00
Purchase #6	$37.35	13.726%	$42.4767	$42.48	$42.50	$42.50
Purchase #7	$141.97	4.543%	$148.4197	$148.42	$148.40	$148.40
7 purchase totals =	$994.58		$1,076.1988	$1,076.21	$1,076.20	$1,076.30