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 $181.47   6.713%   $193.6521   $193.65   $193.65   $193.70  
  Purchase #2 $238.90   9.106%   $260.6542   $260.65   $260.65   $260.70  
  Purchase #3 $94.97   13.735%   $108.0141   $108.01   $108.00   $108.00  
  Purchase #4 $115.88   10.459%   $127.9999   $128.00   $128.00   $128.00  
  Purchase #5 $213.70   10.816%   $236.8138   $236.81   $236.80   $236.80  
  Purchase #6 $16.45   13.868%   $18.7313   $18.73   $18.75   $18.70  
  Purchase #7 $60.56   13.409%   $68.6805   $68.68   $68.70   $68.70  
  7 purchase totals = $921.93       $1,014.5459   $1,014.53   $1,014.55   $1,014.60