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 $85.93   11.655%   $95.9451   $95.95   $95.95   $95.90  
  Purchase #2 $106.93   3.523%   $110.6971   $110.70   $110.70   $110.70  
  Purchase #3 $107.63   4.725%   $112.7155   $112.72   $112.70   $112.70  
  Purchase #4 $177.90   6.466%   $189.403   $189.40   $189.40   $189.40  
  Purchase #5 $191.31   6.780%   $204.2808   $204.28   $204.30   $204.30  
  Purchase #6 $29.28   11.869%   $32.7552   $32.76   $32.75   $32.80  
  Purchase #7 $21.85   10.440%   $24.1311   $24.13   $24.15   $24.10  
  7 purchase totals = $720.83       $769.9278   $769.94   $769.95   $769.90