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 $181.47   7.531%   $195.1365   $195.14   $195.15   $195.10  
  Purchase #2 $210.62   4.356%   $219.7946   $219.79   $219.80   $219.80  
  Purchase #3 $93.47   10.715%   $103.4853   $103.49   $103.50   $103.50  
  Purchase #4 $183.38   4.188%   $191.06   $191.06   $191.05   $191.10  
  Purchase #5 $57.44   5.546%   $60.6256   $60.63   $60.65   $60.60  
  Purchase #6 $38.80   13.253%   $43.9422   $43.94   $43.95   $43.90  
  Purchase #7 $172.45   11.311%   $191.9558   $191.96   $191.95   $192.00  
  7 purchase totals = $937.63       $1,006.0000   $1,006.01   $1,006.05   $1,006.00