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 $152.75   6.679%   $162.9522   $162.95   $162.95   $163.00  
  Purchase #2 $225.56   8.604%   $244.9672   $244.97   $244.95   $245.00  
  Purchase #3 $58.49   5.372%   $61.6321   $61.63   $61.65   $61.60  
  Purchase #4 $30.97   5.147%   $32.564   $32.56   $32.55   $32.60  
  Purchase #5 $231.79   13.828%   $263.8419   $263.84   $263.85   $263.80  
  Purchase #6 $204.28   9.271%   $223.2188   $223.22   $223.20   $223.20  
  Purchase #7 $47.55   3.854%   $49.3826   $49.38   $49.40   $49.40  
  7 purchase totals = $951.39       $1,038.5588   $1,038.55   $1,038.55   $1,038.60