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 $234.38   5.469%   $247.1982   $247.20   $247.20   $247.20  
  Purchase #2 $38.63   6.360%   $41.0869   $41.09   $41.10   $41.10  
  Purchase #3 $102.85   8.237%   $111.3218   $111.32   $111.30   $111.30  
  Purchase #4 $134.76   4.778%   $141.1988   $141.20   $141.20   $141.20  
  Purchase #5 $193.93   3.207%   $200.1493   $200.15   $200.15   $200.10  
  Purchase #6 $174.66   10.399%   $192.8229   $192.82   $192.80   $192.80  
  Purchase #7 $84.79   5.188%   $89.1889   $89.19   $89.20   $89.20  
  7 purchase totals = $964.00       $1,022.9668   $1,022.97   $1,022.95   $1,022.90