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 $58.83   5.808%   $62.2468   $62.25   $62.25   $62.20  
  Purchase #2 $239.89   6.145%   $254.6312   $254.63   $254.65   $254.60  
  Purchase #3 $117.92   5.806%   $124.7664   $124.77   $124.75   $124.80  
  Purchase #4 $241.52   3.590%   $250.1906   $250.19   $250.20   $250.20  
  Purchase #5 $228.49   13.753%   $259.9142   $259.91   $259.90   $259.90  
  Purchase #6 $44.67   10.227%   $49.2384   $49.24   $49.25   $49.20  
  Purchase #7 $31.37   10.866%   $34.7787   $34.78   $34.80   $34.80  
  7 purchase totals = $962.69       $1,035.7663   $1,035.77   $1,035.80   $1,035.70