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 $65.48   9.484%   $71.6901   $71.69   $71.70   $71.70  
  Purchase #2 $200.85   5.110%   $211.1134   $211.11   $211.10   $211.10  
  Purchase #3 $40.99   12.769%   $46.224   $46.22   $46.20   $46.20  
  Purchase #4 $142.80   4.593%   $149.3588   $149.36   $149.35   $149.40  
  Purchase #5 $31.50   9.510%   $34.4957   $34.50   $34.50   $34.50  
  Purchase #6 $33.75   13.605%   $38.3417   $38.34   $38.35   $38.30  
  Purchase #7 $204.87   3.183%   $211.391   $211.39   $211.40   $211.40  
  7 purchase totals = $720.24       $762.6147   $762.61   $762.60   $762.60