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 $46.87   3.846%   $48.6726   $48.67   $48.65   $48.70  
  Purchase #2 $228.33   13.454%   $259.0495   $259.05   $259.05   $259.00  
  Purchase #3 $239.82   6.577%   $255.593   $255.59   $255.60   $255.60  
  Purchase #4 $103.29   3.194%   $106.5891   $106.59   $106.60   $106.60  
  Purchase #5 $128.57   4.342%   $134.1525   $134.15   $134.15   $134.20  
  Purchase #6 $100.83   4.106%   $104.9701   $104.97   $104.95   $105.00  
  Purchase #7 $179.38   7.290%   $192.4568   $192.46   $192.45   $192.50  
  7 purchase totals = $1,027.09       $1,101.4836   $1,101.48   $1,101.45   $1,101.60