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 $114.44   4.544%   $119.6402   $119.64   $119.65   $119.60  
  Purchase #2 $216.76   12.844%   $244.6007   $244.60   $244.60   $244.60  
  Purchase #3 $103.29   10.791%   $114.436   $114.44   $114.45   $114.40  
  Purchase #4 $151.58   7.266%   $162.5938   $162.59   $162.60   $162.60  
  Purchase #5 $235.33   12.499%   $264.7439   $264.74   $264.75   $264.70  
  Purchase #6 $170.86   3.177%   $176.2882   $176.29   $176.30   $176.30  
  Purchase #7 $65.62   10.505%   $72.5134   $72.51   $72.50   $72.50  
  7 purchase totals = $1,057.88       $1,154.8162   $1,154.81   $1,154.85   $1,154.70