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 $95.70   6.266%   $101.6966   $101.70   $101.70   $101.70  
  Purchase #2 $201.98   11.339%   $224.8825   $224.88   $224.90   $224.90  
  Purchase #3 $129.73   5.637%   $137.0429   $137.04   $137.05   $137.00  
  Purchase #4 $65.48   9.265%   $71.5467   $71.55   $71.55   $71.50  
  Purchase #5 $208.62   3.296%   $215.4961   $215.50   $215.50   $215.50  
  Purchase #6 $204.64   6.473%   $217.8863   $217.89   $217.90   $217.90  
  Purchase #7 $54.78   5.379%   $57.7266   $57.73   $57.75   $57.70  
  7 purchase totals = $960.93       $1,026.2777   $1,026.29   $1,026.35   $1,026.20