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 $232.75   8.334%   $252.1474   $252.15   $252.15   $252.10  
  Purchase #2 $209.55   9.104%   $228.6274   $228.63   $228.65   $228.60  
  Purchase #3 $36.62   3.846%   $38.0284   $38.03   $38.05   $38.00  
  Purchase #4 $99.35   11.415%   $110.6908   $110.69   $110.70   $110.70  
  Purchase #5 $24.58   8.309%   $26.6224   $26.62   $26.60   $26.60  
  Purchase #6 $183.98   9.122%   $200.7627   $200.76   $200.75   $200.80  
  Purchase #7 $236.60   6.138%   $251.1225   $251.12   $251.10   $251.10  
  7 purchase totals = $1,023.43       $1,108.0016   $1,108.00   $1,108.00   $1,107.90