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	$224.97	9.803%	$247.0238	$247.02	$247.00	$247.00
Purchase #2	$15.69	13.297%	$17.7763	$17.78	$17.80	$17.80
Purchase #3	$40.78	3.478%	$42.1983	$42.20	$42.20	$42.20
Purchase #4	$218.31	4.205%	$227.4899	$227.49	$227.50	$227.50
Purchase #5	$164.80	4.870%	$172.8258	$172.83	$172.85	$172.80
Purchase #6	$156.30	8.578%	$169.7074	$169.71	$169.70	$169.70
Purchase #7	$189.42	12.159%	$212.4516	$212.45	$212.45	$212.50
7 purchase totals =	$1,010.27		$1,089.4731	$1,089.48	$1,089.50	$1,089.50