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 $178.55   5.295%   $188.0042   $188.00   $188.00   $188.00  
  Purchase #2 $89.85   5.395%   $94.6974   $94.70   $94.70   $94.70  
  Purchase #3 $67.44   6.683%   $71.947   $71.95   $71.95   $71.90  
  Purchase #4 $236.65   10.566%   $261.6544   $261.65   $261.65   $261.70  
  Purchase #5 $87.43   10.404%   $96.5262   $96.53   $96.55   $96.50  
  Purchase #6 $88.72   6.249%   $94.2641   $94.26   $94.25   $94.30  
  Purchase #7 $205.93   6.177%   $218.6503   $218.65   $218.65   $218.70  
  7 purchase totals = $954.57       $1,025.7436   $1,025.74   $1,025.75   $1,025.80