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 $61.43   3.554%   $63.6132   $63.61   $63.60   $63.60  
  Purchase #2 $200.46   9.451%   $219.4055   $219.41   $219.40   $219.40  
  Purchase #3 $234.89   12.118%   $263.354   $263.35   $263.35   $263.40  
  Purchase #4 $238.78   3.526%   $247.1994   $247.20   $247.20   $247.20  
  Purchase #5 $118.29   6.339%   $125.7884   $125.79   $125.80   $125.80  
  Purchase #6 $197.88   13.141%   $223.8834   $223.88   $223.90   $223.90  
  Purchase #7 $32.87   6.539%   $35.0194   $35.02   $35.00   $35.00  
  7 purchase totals = $1,084.60       $1,178.2633   $1,178.26   $1,178.25   $1,178.30