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 $208.83   11.511%   $232.8684   $232.87   $232.85   $232.90  
  Purchase #2 $154.30   6.195%   $163.8589   $163.86   $163.85   $163.90  
  Purchase #3 $187.53   8.364%   $203.215   $203.22   $203.20   $203.20  
  Purchase #4 $69.38   3.340%   $71.6973   $71.70   $71.70   $71.70  
  Purchase #5 $206.64   5.652%   $218.3193   $218.32   $218.30   $218.30  
  Purchase #6 $154.55   10.246%   $170.3852   $170.39   $170.40   $170.40  
  Purchase #7 $195.96   5.428%   $206.5967   $206.60   $206.60   $206.60  
  7 purchase totals = $1,177.19       $1,266.9408   $1,266.96   $1,266.90   $1,267.00