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	$237.92	7.665%	$256.1566	$256.16	$256.15	$256.20
Purchase #2	$157.42	10.733%	$174.3159	$174.32	$174.30	$174.30
Purchase #3	$91.38	4.357%	$95.3614	$95.36	$95.35	$95.40
Purchase #4	$215.34	6.386%	$229.0916	$229.09	$229.10	$229.10
Purchase #5	$31.86	6.430%	$33.9086	$33.91	$33.90	$33.90
Purchase #6	$246.38	13.852%	$280.5086	$280.51	$280.50	$280.50
Purchase #7	$206.73	5.635%	$218.3792	$218.38	$218.40	$218.40
7 purchase totals =	$1,187.03		$1,287.7219	$1,287.73	$1,287.70	$1,287.80