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 $141.75   7.282%   $152.0722   $152.07   $152.05   $152.10  
  Purchase #2 $150.99   10.765%   $167.2441   $167.24   $167.25   $167.20  
  Purchase #3 $59.29   9.234%   $64.7648   $64.76   $64.75   $64.80  
  Purchase #4 $181.71   8.683%   $197.4879   $197.49   $197.50   $197.50  
  Purchase #5 $51.69   13.442%   $58.6382   $58.64   $58.65   $58.60  
  Purchase #6 $162.55   8.652%   $176.6138   $176.61   $176.60   $176.60  
  Purchase #7 $148.82   5.118%   $156.4366   $156.44   $156.45   $156.40  
  7 purchase totals = $896.80       $973.2576   $973.25   $973.25   $973.20