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 $67.71   8.869%   $73.7152   $73.72   $73.70   $73.70  
  Purchase #2 $218.75   8.638%   $237.6456   $237.65   $237.65   $237.60  
  Purchase #3 $75.98   13.842%   $86.4972   $86.50   $86.50   $86.50  
  Purchase #4 $162.27   6.527%   $172.8614   $172.86   $172.85   $172.90  
  Purchase #5 $135.88   5.601%   $143.4906   $143.49   $143.50   $143.50  
  Purchase #6 $89.74   6.831%   $95.8701   $95.87   $95.85   $95.90  
  Purchase #7 $129.81   9.472%   $142.1056   $142.11   $142.10   $142.10  
  7 purchase totals = $880.14       $952.1857   $952.20   $952.15   $952.20