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 $161.66   4.614%   $169.119   $169.12   $169.10   $169.10  
  Purchase #2 $140.67   11.571%   $156.9469   $156.95   $156.95   $156.90  
  Purchase #3 $73.32   12.711%   $82.6397   $82.64   $82.65   $82.60  
  Purchase #4 $29.54   8.282%   $31.9865   $31.99   $32.00   $32.00  
  Purchase #5 $160.60   9.420%   $175.7285   $175.73   $175.75   $175.70  
  Purchase #6 $223.66   4.769%   $234.3263   $234.33   $234.35   $234.30  
  Purchase #7 $185.80   4.492%   $194.1461   $194.15   $194.15   $194.10  
  7 purchase totals = $975.25       $1,044.8930   $1,044.91   $1,044.95   $1,044.70