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 $184.46   11.669%   $205.9846   $205.98   $206.00   $206.00  
  Purchase #2 $219.85   10.398%   $242.71   $242.71   $242.70   $242.70  
  Purchase #3 $188.58   13.483%   $214.0062   $214.01   $214.00   $214.00  
  Purchase #4 $146.39   3.270%   $151.177   $151.18   $151.20   $151.20  
  Purchase #5 $112.34   7.714%   $121.0059   $121.01   $121.00   $121.00  
  Purchase #6 $37.89   7.395%   $40.692   $40.69   $40.70   $40.70  
  Purchase #7 $157.68   10.701%   $174.5533   $174.55   $174.55   $174.60  
  7 purchase totals = $1,047.19       $1,150.1290   $1,150.13   $1,150.15   $1,150.20