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 $33.77   5.134%   $35.5038   $35.50   $35.50   $35.50  
  Purchase #2 $224.29   9.411%   $245.3979   $245.40   $245.40   $245.40  
  Purchase #3 $59.94   4.289%   $62.5108   $62.51   $62.50   $62.50  
  Purchase #4 $187.39   5.507%   $197.7096   $197.71   $197.70   $197.70  
  Purchase #5 $188.54   11.849%   $210.8801   $210.88   $210.90   $210.90  
  Purchase #6 $171.60   4.658%   $179.5931   $179.59   $179.60   $179.60  
  Purchase #7 $157.31   11.653%   $175.6413   $175.64   $175.65   $175.60  
  7 purchase totals = $1,022.84       $1,107.2366   $1,107.23   $1,107.25   $1,107.20