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 $60.75   11.871%   $67.9616   $67.96   $67.95   $68.00  
  Purchase #2 $9.80   9.622%   $10.743   $10.74   $10.75   $10.70  
  Purchase #3 $27.76   4.623%   $29.0433   $29.04   $29.05   $29.00  
  Purchase #4 $53.65   7.506%   $57.677   $57.68   $57.70   $57.70  
  Purchase #5 $89.30   10.725%   $98.8774   $98.88   $98.90   $98.90  
  Purchase #6 $228.27   5.599%   $241.0508   $241.05   $241.05   $241.10  
  Purchase #7 $237.31   11.186%   $263.8555   $263.86   $263.85   $263.90  
  7 purchase totals = $706.84       $769.2086   $769.21   $769.25   $769.30