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 $44.70   5.751%   $47.2707   $47.27   $47.25   $47.30  
  Purchase #2 $236.67   11.333%   $263.4918   $263.49   $263.50   $263.50  
  Purchase #3 $150.72   8.664%   $163.7784   $163.78   $163.80   $163.80  
  Purchase #4 $224.78   3.446%   $232.5259   $232.53   $232.55   $232.50  
  Purchase #5 $90.36   5.301%   $95.15   $95.15   $95.15   $95.20  
  Purchase #6 $38.52   11.638%   $43.003   $43.00   $43.00   $43.00  
  Purchase #7 $138.45   8.117%   $149.688   $149.69   $149.70   $149.70  
  7 purchase totals = $924.20       $994.9078   $994.91   $994.95   $995.00