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 $54.54   13.414%   $61.856   $61.86   $61.85   $61.90  
  Purchase #2 $206.73   8.384%   $224.0622   $224.06   $224.05   $224.10  
  Purchase #3 $85.53   8.760%   $93.0224   $93.02   $93.00   $93.00  
  Purchase #4 $25.68   8.161%   $27.7757   $27.78   $27.80   $27.80  
  Purchase #5 $91.50   6.667%   $97.6003   $97.60   $97.60   $97.60  
  Purchase #6 $69.29   6.647%   $73.8957   $73.90   $73.90   $73.90  
  Purchase #7 $243.79   10.172%   $268.5883   $268.59   $268.60   $268.60  
  7 purchase totals = $777.06       $846.8006   $846.81   $846.80   $846.90