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 $212.25   11.719%   $237.1236   $237.12   $237.10   $237.10  
  Purchase #2 $23.69   5.313%   $24.9486   $24.95   $24.95   $24.90  
  Purchase #3 $180.49   4.296%   $188.2439   $188.24   $188.25   $188.20  
  Purchase #4 $68.75   4.256%   $71.676   $71.68   $71.70   $71.70  
  Purchase #5 $198.68   10.814%   $220.1653   $220.17   $220.15   $220.20  
  Purchase #6 $215.91   13.871%   $245.8589   $245.86   $245.85   $245.90  
  Purchase #7 $54.65   5.320%   $57.5574   $57.56   $57.55   $57.60  
  7 purchase totals = $954.42       $1,045.5737   $1,045.58   $1,045.55   $1,045.60