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	$199.67	11.321%	$222.2746	$222.27	$222.25	$222.30
Purchase #2	$33.59	10.282%	$37.0437	$37.04	$37.05	$37.00
Purchase #3	$145.47	12.224%	$163.2523	$163.25	$163.25	$163.30
Purchase #4	$82.32	8.411%	$89.2439	$89.24	$89.25	$89.20
Purchase #5	$223.90	13.382%	$253.8623	$253.86	$253.85	$253.90
Purchase #6	$225.60	5.775%	$238.6284	$238.63	$238.65	$238.60
Purchase #7	$11.55	13.441%	$13.1024	$13.10	$13.10	$13.10
7 purchase totals =	$922.10		$1,017.4076	$1,017.39	$1,017.40	$1,017.40