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 $217.66   8.146%   $235.3906   $235.39   $235.40   $235.40  
  Purchase #2 $38.62   11.769%   $43.1652   $43.17   $43.15   $43.20  
  Purchase #3 $117.88   12.746%   $132.905   $132.91   $132.90   $132.90  
  Purchase #4 $125.63   8.479%   $136.2822   $136.28   $136.30   $136.30  
  Purchase #5 $173.34   12.861%   $195.6333   $195.63   $195.65   $195.60  
  Purchase #6 $49.60   8.599%   $53.8651   $53.87   $53.85   $53.90  
  Purchase #7 $199.32   8.774%   $216.8083   $216.81   $216.80   $216.80  
  7 purchase totals = $922.05       $1,014.0497   $1,014.06   $1,014.05   $1,014.10