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 $85.69   12.324%   $96.2504   $96.25   $96.25   $96.30  
  Purchase #2 $117.33   12.771%   $132.3142   $132.31   $132.30   $132.30  
  Purchase #3 $193.74   8.332%   $209.8824   $209.88   $209.90   $209.90  
  Purchase #4 $136.84   6.688%   $145.9919   $145.99   $146.00   $146.00  
  Purchase #5 $73.36   5.812%   $77.6237   $77.62   $77.60   $77.60  
  Purchase #6 $238.25   10.297%   $262.7826   $262.78   $262.80   $262.80  
  Purchase #7 $125.47   7.205%   $134.5101   $134.51   $134.50   $134.50  
  7 purchase totals = $970.68       $1,059.3553   $1,059.34   $1,059.35   $1,059.40