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 $232.47   12.563%   $261.6752   $261.68   $261.70   $261.70  
  Purchase #2 $101.59   12.171%   $113.9545   $113.95   $113.95   $114.00  
  Purchase #3 $180.30   11.670%   $201.341   $201.34   $201.35   $201.30  
  Purchase #4 $84.27   12.868%   $95.1139   $95.11   $95.10   $95.10  
  Purchase #5 $121.64   11.324%   $135.4145   $135.41   $135.40   $135.40  
  Purchase #6 $146.99   5.803%   $155.5198   $155.52   $155.50   $155.50  
  Purchase #7 $59.84   3.650%   $62.0242   $62.02   $62.00   $62.00  
  7 purchase totals = $927.10       $1,025.0431   $1,025.03   $1,025.00   $1,025.00