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 $83.91   11.324%   $93.412   $93.41   $93.40   $93.40  
  Purchase #2 $157.33   11.304%   $175.1146   $175.11   $175.10   $175.10  
  Purchase #3 $88.72   11.436%   $98.866   $98.87   $98.85   $98.90  
  Purchase #4 $190.78   6.636%   $203.4402   $203.44   $203.45   $203.40  
  Purchase #5 $12.81   7.248%   $13.7385   $13.74   $13.75   $13.70  
  Purchase #6 $48.61   9.242%   $53.1025   $53.10   $53.10   $53.10  
  Purchase #7 $121.66   10.466%   $134.3929   $134.39   $134.40   $134.40  
  7 purchase totals = $703.82       $772.0667   $772.06   $772.05   $772.00