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 $62.81   13.723%   $71.4294   $71.43   $71.45   $71.40  
  Purchase #2 $83.66   13.514%   $94.9658   $94.97   $94.95   $95.00  
  Purchase #3 $93.64   11.329%   $104.2485   $104.25   $104.25   $104.20  
  Purchase #4 $87.43   10.563%   $96.6652   $96.67   $96.65   $96.70  
  Purchase #5 $111.45   12.341%   $125.204   $125.20   $125.20   $125.20  
  Purchase #6 $180.27   13.595%   $204.7777   $204.78   $204.80   $204.80  
  Purchase #7 $45.73   6.112%   $48.525   $48.53   $48.55   $48.50  
  7 purchase totals = $664.99       $745.8156   $745.83   $745.85   $745.80