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 $24.78   5.689%   $26.1897   $26.19   $26.20   $26.20  
  Purchase #2 $60.36   7.822%   $65.0814   $65.08   $65.10   $65.10  
  Purchase #3 $141.39   10.697%   $156.5145   $156.51   $156.50   $156.50  
  Purchase #4 $181.34   8.113%   $196.0521   $196.05   $196.05   $196.10  
  Purchase #5 $19.69   11.234%   $21.902   $21.90   $21.90   $21.90  
  Purchase #6 $243.47   10.345%   $268.657   $268.66   $268.65   $268.70  
  Purchase #7 $180.58   5.593%   $190.6798   $190.68   $190.70   $190.70  
  7 purchase totals = $851.61       $925.0765   $925.07   $925.10   $925.20