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 $88.50   9.556%   $96.9571   $96.96   $96.95   $97.00  
  Purchase #2 $210.80   5.572%   $222.5458   $222.55   $222.55   $222.50  
  Purchase #3 $194.96   12.152%   $218.6515   $218.65   $218.65   $218.70  
  Purchase #4 $233.44   4.462%   $243.8561   $243.86   $243.85   $243.90  
  Purchase #5 $245.89   6.462%   $261.7794   $261.78   $261.80   $261.80  
  Purchase #6 $46.88   7.227%   $50.268   $50.27   $50.25   $50.30  
  Purchase #7 $9.42   12.285%   $10.5772   $10.58   $10.60   $10.60  
  7 purchase totals = $1,029.89       $1,104.6351   $1,104.65   $1,104.65   $1,104.80