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 $59.68   13.277%   $67.6037   $67.60   $67.60   $67.60  
  Purchase #2 $146.29   10.702%   $161.946   $161.95   $161.95   $161.90  
  Purchase #3 $61.87   10.870%   $68.5953   $68.60   $68.60   $68.60  
  Purchase #4 $158.42   3.359%   $163.7413   $163.74   $163.75   $163.70  
  Purchase #5 $197.38   11.371%   $219.8241   $219.82   $219.80   $219.80  
  Purchase #6 $138.59   12.462%   $155.8611   $155.86   $155.85   $155.90  
  Purchase #7 $224.41   6.394%   $238.7588   $238.76   $238.75   $238.80  
  7 purchase totals = $986.64       $1,076.3303   $1,076.33   $1,076.30   $1,076.30