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 $96.37   8.645%   $104.7012   $104.70   $104.70   $104.70  
  Purchase #2 $223.35   4.171%   $232.6659   $232.67   $232.65   $232.70  
  Purchase #3 $178.34   13.184%   $201.8523   $201.85   $201.85   $201.90  
  Purchase #4 $174.60   10.323%   $192.624   $192.62   $192.60   $192.60  
  Purchase #5 $222.43   6.856%   $237.6798   $237.68   $237.70   $237.70  
  Purchase #6 $189.72   10.312%   $209.2839   $209.28   $209.30   $209.30  
  Purchase #7 $158.91   12.808%   $179.2632   $179.26   $179.25   $179.30  
  7 purchase totals = $1,243.72       $1,358.0703   $1,358.06   $1,358.05   $1,358.20