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 $196.79   13.627%   $223.6066   $223.61   $223.60   $223.60  
  Purchase #2 $106.72   10.207%   $117.6129   $117.61   $117.60   $117.60  
  Purchase #3 $203.47   5.532%   $214.726   $214.73   $214.75   $214.70  
  Purchase #4 $136.80   3.522%   $141.6181   $141.62   $141.60   $141.60  
  Purchase #5 $61.31   5.805%   $64.869   $64.87   $64.85   $64.90  
  Purchase #6 $185.76   9.271%   $202.9818   $202.98   $203.00   $203.00  
  Purchase #7 $202.65   13.328%   $229.6592   $229.66   $229.65   $229.70  
  7 purchase totals = $1,093.50       $1,195.0736   $1,195.08   $1,195.05   $1,195.10