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 $24.81   5.790%   $26.2465   $26.25   $26.25   $26.20  
  Purchase #2 $215.90   5.140%   $226.9973   $227.00   $227.00   $227.00  
  Purchase #3 $65.73   3.398%   $67.9635   $67.96   $67.95   $68.00  
  Purchase #4 $146.65   3.230%   $151.3868   $151.39   $151.40   $151.40  
  Purchase #5 $45.90   13.438%   $52.068   $52.07   $52.05   $52.10  
  Purchase #6 $169.36   10.138%   $186.5297   $186.53   $186.55   $186.50  
  Purchase #7 $246.43   7.618%   $265.203   $265.20   $265.20   $265.20  
  7 purchase totals = $914.78       $976.3948   $976.40   $976.40   $976.40