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 $213.83   11.202%   $237.7832   $237.78   $237.80   $237.80  
  Purchase #2 $74.56   10.771%   $82.5909   $82.59   $82.60   $82.60  
  Purchase #3 $228.59   7.358%   $245.4097   $245.41   $245.40   $245.40  
  Purchase #4 $250.31   5.590%   $264.3023   $264.30   $264.30   $264.30  
  Purchase #5 $121.90   10.435%   $134.6203   $134.62   $134.60   $134.60  
  Purchase #6 $23.87   10.801%   $26.4482   $26.45   $26.45   $26.40  
  Purchase #7 $97.96   6.377%   $104.2069   $104.21   $104.20   $104.20  
  7 purchase totals = $1,011.02       $1,095.3615   $1,095.36   $1,095.35   $1,095.30