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 $83.96   12.120%   $94.136   $94.14   $94.15   $94.10  
  Purchase #2 $148.57   12.626%   $167.3284   $167.33   $167.35   $167.30  
  Purchase #3 $228.48   8.656%   $248.2572   $248.26   $248.25   $248.30  
  Purchase #4 $92.88   5.529%   $98.0153   $98.02   $98.00   $98.00  
  Purchase #5 $154.92   3.870%   $160.9154   $160.92   $160.90   $160.90  
  Purchase #6 $213.48   11.710%   $238.4785   $238.48   $238.50   $238.50  
  Purchase #7 $157.25   10.376%   $173.5663   $173.57   $173.55   $173.60  
  7 purchase totals = $1,079.54       $1,180.6971   $1,180.72   $1,180.70   $1,180.70