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 $235.45   11.292%   $262.037   $262.04   $262.05   $262.00  
  Purchase #2 $142.34   12.691%   $160.4044   $160.40   $160.40   $160.40  
  Purchase #3 $106.79   6.377%   $113.6   $113.60   $113.60   $113.60  
  Purchase #4 $64.53   7.629%   $69.453   $69.45   $69.45   $69.50  
  Purchase #5 $31.75   12.347%   $35.6702   $35.67   $35.65   $35.70  
  Purchase #6 $151.38   11.131%   $168.2301   $168.23   $168.25   $168.20  
  Purchase #7 $145.98   4.383%   $152.3783   $152.38   $152.40   $152.40  
  7 purchase totals = $878.22       $961.7730   $961.77   $961.80   $961.80