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 $92.33   13.698%   $104.9774   $104.98   $105.00   $105.00  
  Purchase #2 $161.39   13.158%   $182.6257   $182.63   $182.65   $182.60  
  Purchase #3 $123.54   5.795%   $130.6991   $130.70   $130.70   $130.70  
  Purchase #4 $201.26   7.250%   $215.8514   $215.85   $215.85   $215.90  
  Purchase #5 $10.69   4.871%   $11.2107   $11.21   $11.20   $11.20  
  Purchase #6 $211.36   12.775%   $238.3612   $238.36   $238.35   $238.40  
  Purchase #7 $192.92   12.761%   $217.5385   $217.54   $217.55   $217.50  
  7 purchase totals = $993.49       $1,101.2640   $1,101.27   $1,101.30   $1,101.30