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 $215.48   13.697%   $244.9943   $244.99   $245.00   $245.00  
  Purchase #2 $208.43   8.720%   $226.6051   $226.61   $226.60   $226.60  
  Purchase #3 $39.93   5.706%   $42.2084   $42.21   $42.20   $42.20  
  Purchase #4 $33.64   5.601%   $35.5242   $35.52   $35.50   $35.50  
  Purchase #5 $23.47   6.593%   $25.0174   $25.02   $25.00   $25.00  
  Purchase #6 $50.86   6.136%   $53.9808   $53.98   $54.00   $54.00  
  Purchase #7 $92.34   12.840%   $104.1965   $104.20   $104.20   $104.20  
  7 purchase totals = $664.15       $732.5267   $732.53   $732.50   $732.50