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 $197.95   8.126%   $214.0354   $214.04   $214.05   $214.00  
  Purchase #2 $34.32   10.754%   $38.0108   $38.01   $38.00   $38.00  
  Purchase #3 $200.73   6.109%   $212.9926   $212.99   $213.00   $213.00  
  Purchase #4 $236.36   7.703%   $254.5668   $254.57   $254.55   $254.60  
  Purchase #5 $60.36   4.478%   $63.0629   $63.06   $63.05   $63.10  
  Purchase #6 $146.59   12.345%   $164.6865   $164.69   $164.70   $164.70  
  Purchase #7 $72.27   9.717%   $79.2925   $79.29   $79.30   $79.30  
  7 purchase totals = $948.58       $1,026.6475   $1,026.65   $1,026.65   $1,026.70