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 $62.30   10.682%   $68.9549   $68.95   $68.95   $69.00  
  Purchase #2 $207.87   6.532%   $221.4481   $221.45   $221.45   $221.40  
  Purchase #3 $157.57   13.701%   $179.1587   $179.16   $179.15   $179.20  
  Purchase #4 $123.29   10.784%   $136.5856   $136.59   $136.60   $136.60  
  Purchase #5 $219.62   11.596%   $245.0871   $245.09   $245.10   $245.10  
  Purchase #6 $122.71   10.334%   $135.3909   $135.39   $135.40   $135.40  
  Purchase #7 $41.87   6.334%   $44.522   $44.52   $44.50   $44.50  
  7 purchase totals = $935.23       $1,031.1473   $1,031.15   $1,031.15   $1,031.20