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 $44.33   3.776%   $46.0039   $46.00   $46.00   $46.00  
  Purchase #2 $232.77   9.291%   $254.3967   $254.40   $254.40   $254.40  
  Purchase #3 $214.54   5.693%   $226.7538   $226.75   $226.75   $226.80  
  Purchase #4 $56.85   13.257%   $64.3866   $64.39   $64.40   $64.40  
  Purchase #5 $82.28   4.725%   $86.1677   $86.17   $86.15   $86.20  
  Purchase #6 $95.61   13.507%   $108.524   $108.52   $108.50   $108.50  
  Purchase #7 $211.28   7.765%   $227.6859   $227.69   $227.70   $227.70  
  7 purchase totals = $937.66       $1,013.9186   $1,013.92   $1,013.90   $1,014.00