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 $45.81   7.661%   $49.3195   $49.32   $49.30   $49.30  
  Purchase #2 $234.87   11.669%   $262.277   $262.28   $262.30   $262.30  
  Purchase #3 $146.85   13.762%   $167.0595   $167.06   $167.05   $167.10  
  Purchase #4 $62.44   10.545%   $69.0243   $69.02   $69.00   $69.00  
  Purchase #5 $6.89   11.383%   $7.6743   $7.67   $7.65   $7.70  
  Purchase #6 $205.77   3.570%   $213.116   $213.12   $213.10   $213.10  
  Purchase #7 $160.33   9.547%   $175.6367   $175.64   $175.65   $175.60  
  7 purchase totals = $862.96       $944.1073   $944.11   $944.05   $944.10