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	$77.68	6.149%	$82.4565	$82.46	$82.45	$82.50
Purchase #2	$34.85	5.256%	$36.6817	$36.68	$36.70	$36.70
Purchase #3	$32.68	13.537%	$37.1039	$37.10	$37.10	$37.10
Purchase #4	$199.34	5.191%	$209.6877	$209.69	$209.70	$209.70
Purchase #5	$39.47	9.662%	$43.2836	$43.28	$43.30	$43.30
Purchase #6	$196.60	10.249%	$216.7495	$216.75	$216.75	$216.70
Purchase #7	$128.69	9.505%	$140.922	$140.92	$140.90	$140.90
7 purchase totals =	$709.31		$766.8849	$766.88	$766.90	$766.90