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	$211.31	3.351%	$218.391	$218.39	$218.40	$218.40
Purchase #2	$218.57	9.591%	$239.533	$239.53	$239.55	$239.50
Purchase #3	$80.35	12.738%	$90.585	$90.59	$90.60	$90.60
Purchase #4	$81.47	9.756%	$89.4182	$89.42	$89.40	$89.40
Purchase #5	$208.70	4.209%	$217.4842	$217.48	$217.50	$217.50
Purchase #6	$168.56	13.320%	$191.0122	$191.01	$191.00	$191.00
Purchase #7	$76.64	3.837%	$79.5807	$79.58	$79.60	$79.60
7 purchase totals =	$1,045.60		$1,126.0043	$1,126.00	$1,126.05	$1,126.00