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	$227.56	11.767%	$254.337	$254.34	$254.35	$254.30
Purchase #2	$31.67	4.282%	$33.0261	$33.03	$33.05	$33.00
Purchase #3	$91.43	8.553%	$99.25	$99.25	$99.25	$99.30
Purchase #4	$18.99	10.572%	$20.9976	$21.00	$21.00	$21.00
Purchase #5	$225.89	7.366%	$242.5291	$242.53	$242.55	$242.50
Purchase #6	$237.99	13.619%	$270.4019	$270.40	$270.40	$270.40
Purchase #7	$234.38	10.701%	$259.461	$259.46	$259.45	$259.50
7 purchase totals =	$1,067.91		$1,180.0027	$1,180.01	$1,180.05	$1,180.00