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 $181.95   7.533%   $195.6563   $195.66   $195.65   $195.70  
  Purchase #2 $135.93   4.870%   $142.5498   $142.55   $142.55   $142.50  
  Purchase #3 $200.44   7.841%   $216.1565   $216.16   $216.15   $216.20  
  Purchase #4 $33.53   8.443%   $36.3609   $36.36   $36.35   $36.40  
  Purchase #5 $46.67   13.236%   $52.8472   $52.85   $52.85   $52.80  
  Purchase #6 $46.30   10.530%   $51.1754   $51.18   $51.20   $51.20  
  Purchase #7 $28.74   4.849%   $30.1336   $30.13   $30.15   $30.10  
  7 purchase totals = $673.56       $724.8797   $724.89   $724.90   $724.90