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 $118.94   6.690%   $126.8971   $126.90   $126.90   $126.90  
  Purchase #2 $35.25   11.816%   $39.4151   $39.42   $39.40   $39.40  
  Purchase #3 $148.55   8.861%   $161.713   $161.71   $161.70   $161.70  
  Purchase #4 $201.36   7.518%   $216.4982   $216.50   $216.50   $216.50  
  Purchase #5 $224.81   4.712%   $235.403   $235.40   $235.40   $235.40  
  Purchase #6 $61.39   7.199%   $65.8095   $65.81   $65.80   $65.80  
  Purchase #7 $222.50   12.125%   $249.4781   $249.48   $249.50   $249.50  
  7 purchase totals = $1,012.80       $1,095.2140   $1,095.22   $1,095.20   $1,095.20