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 $86.40   8.465%   $93.7138   $93.71   $93.70   $93.70  
  Purchase #2 $179.50   6.657%   $191.4493   $191.45   $191.45   $191.40  
  Purchase #3 $166.37   5.507%   $175.532   $175.53   $175.55   $175.50  
  Purchase #4 $52.46   8.719%   $57.034   $57.03   $57.05   $57.00  
  Purchase #5 $216.73   5.532%   $228.7195   $228.72   $228.70   $228.70  
  Purchase #6 $192.63   7.259%   $206.613   $206.61   $206.60   $206.60  
  Purchase #7 $211.55   8.255%   $229.0135   $229.01   $229.00   $229.00  
  7 purchase totals = $1,105.64       $1,182.0751   $1,182.06   $1,182.05   $1,181.90