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 $203.39   6.175%   $215.9493   $215.95   $215.95   $215.90  
  Purchase #2 $35.88   6.843%   $38.3353   $38.34   $38.35   $38.30  
  Purchase #3 $80.53   6.233%   $85.5494   $85.55   $85.55   $85.50  
  Purchase #4 $205.30   7.749%   $221.2087   $221.21   $221.20   $221.20  
  Purchase #5 $62.73   3.129%   $64.6928   $64.69   $64.70   $64.70  
  Purchase #6 $228.93   6.452%   $243.7006   $243.70   $243.70   $243.70  
  Purchase #7 $151.70   3.312%   $156.7243   $156.72   $156.70   $156.70  
  7 purchase totals = $968.46       $1,026.1604   $1,026.16   $1,026.15   $1,026.00