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	$218.54	4.594%	$228.5797	$228.58	$228.60	$228.60
Purchase #2	$80.85	12.397%	$90.873	$90.87	$90.85	$90.90
Purchase #3	$123.84	5.559%	$130.7243	$130.72	$130.70	$130.70
Purchase #4	$37.79	7.423%	$40.5952	$40.60	$40.60	$40.60
Purchase #5	$38.98	6.726%	$41.6018	$41.60	$41.60	$41.60
Purchase #6	$239.90	7.856%	$258.7465	$258.75	$258.75	$258.70
Purchase #7	$84.67	11.320%	$94.2546	$94.25	$94.25	$94.30
7 purchase totals =	$824.57		$885.3751	$885.37	$885.35	$885.40