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 $125.47   3.620%   $130.012   $130.01   $130.00   $130.00  
  Purchase #2 $222.55   8.402%   $241.2487   $241.25   $241.25   $241.20  
  Purchase #3 $73.51   4.820%   $77.0532   $77.05   $77.05   $77.10  
  Purchase #4 $93.63   4.406%   $97.7553   $97.76   $97.75   $97.80  
  Purchase #5 $112.77   3.788%   $117.0417   $117.04   $117.05   $117.00  
  Purchase #6 $164.79   3.582%   $170.6928   $170.69   $170.70   $170.70  
  Purchase #7 $191.27   5.804%   $202.3713   $202.37   $202.35   $202.40  
  7 purchase totals = $983.99       $1,036.1750   $1,036.17   $1,036.15   $1,036.20