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 $176.60   10.609%   $195.3355   $195.34   $195.35   $195.30  
  Purchase #2 $111.35   6.108%   $118.1513   $118.15   $118.15   $118.20  
  Purchase #3 $97.27   7.615%   $104.6771   $104.68   $104.70   $104.70  
  Purchase #4 $64.60   5.584%   $68.2073   $68.21   $68.20   $68.20  
  Purchase #5 $90.77   12.748%   $102.3414   $102.34   $102.35   $102.30  
  Purchase #6 $227.44   11.455%   $253.4933   $253.49   $253.50   $253.50  
  Purchase #7 $235.82   12.581%   $265.4885   $265.49   $265.50   $265.50  
  7 purchase totals = $1,003.85       $1,107.6944   $1,107.70   $1,107.75   $1,107.70