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	$229.98	8.239%	$248.9281	$248.93	$248.95	$248.90
Purchase #2	$133.31	5.807%	$141.0513	$141.05	$141.05	$141.10
Purchase #3	$188.99	10.841%	$209.4784	$209.48	$209.50	$209.50
Purchase #4	$53.47	7.198%	$57.3188	$57.32	$57.30	$57.30
Purchase #5	$206.77	4.266%	$215.5908	$215.59	$215.60	$215.60
Purchase #6	$83.43	9.757%	$91.5703	$91.57	$91.55	$91.60
Purchase #7	$206.72	12.446%	$232.4484	$232.45	$232.45	$232.40
7 purchase totals =	$1,102.67		$1,196.3861	$1,196.39	$1,196.40	$1,196.40