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 $85.84   10.348%   $94.7227   $94.72   $94.70   $94.70  
  Purchase #2 $65.64   13.539%   $74.527   $74.53   $74.55   $74.50  
  Purchase #3 $180.76   11.685%   $201.8818   $201.88   $201.90   $201.90  
  Purchase #4 $224.86   7.443%   $241.5963   $241.60   $241.60   $241.60  
  Purchase #5 $58.69   12.455%   $65.9998   $66.00   $66.00   $66.00  
  Purchase #6 $47.59   13.853%   $54.1826   $54.18   $54.20   $54.20  
  Purchase #7 $26.64   10.757%   $29.5057   $29.51   $29.50   $29.50  
  7 purchase totals = $690.02       $762.4159   $762.42   $762.45   $762.40