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 $195.56   6.686%   $208.6351   $208.64   $208.65   $208.60  
  Purchase #2 $67.76   7.776%   $73.029   $73.03   $73.05   $73.00  
  Purchase #3 $151.58   10.576%   $167.6111   $167.61   $167.60   $167.60  
  Purchase #4 $244.52   7.645%   $263.2136   $263.21   $263.20   $263.20  
  Purchase #5 $168.49   6.699%   $179.7771   $179.78   $179.80   $179.80  
  Purchase #6 $51.61   9.661%   $56.596   $56.60   $56.60   $56.60  
  Purchase #7 $87.51   9.525%   $95.8453   $95.85   $95.85   $95.80  
  7 purchase totals = $967.03       $1,044.7072   $1,044.72   $1,044.75   $1,044.60