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 $67.95   8.457%   $73.6965   $73.70   $73.70   $73.70  
  Purchase #2 $31.64   8.206%   $34.2364   $34.24   $34.25   $34.20  
  Purchase #3 $173.44   10.616%   $191.8524   $191.85   $191.85   $191.90  
  Purchase #4 $232.48   3.822%   $241.3654   $241.37   $241.35   $241.40  
  Purchase #5 $47.45   11.531%   $52.9215   $52.92   $52.90   $52.90  
  Purchase #6 $49.76   13.641%   $56.5478   $56.55   $56.55   $56.50  
  Purchase #7 $105.35   5.322%   $110.9567   $110.96   $110.95   $111.00  
  7 purchase totals = $708.07       $761.5767   $761.59   $761.55   $761.60