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 $56.80   9.445%   $62.1648   $62.16   $62.15   $62.20  
  Purchase #2 $108.65   9.796%   $119.2934   $119.29   $119.30   $119.30  
  Purchase #3 $152.73   12.224%   $171.3997   $171.40   $171.40   $171.40  
  Purchase #4 $151.80   3.228%   $156.7001   $156.70   $156.70   $156.70  
  Purchase #5 $205.72   4.482%   $214.9404   $214.94   $214.95   $214.90  
  Purchase #6 $142.79   8.401%   $154.7858   $154.79   $154.80   $154.80  
  Purchase #7 $5.67   5.302%   $5.9706   $5.97   $5.95   $6.00  
  7 purchase totals = $824.16       $885.2548   $885.25   $885.25   $885.30