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 $188.29   9.204%   $205.6202   $205.62   $205.60   $205.60  
  Purchase #2 $151.33   6.852%   $161.6991   $161.70   $161.70   $161.70  
  Purchase #3 $118.88   5.810%   $125.7869   $125.79   $125.80   $125.80  
  Purchase #4 $42.68   9.581%   $46.7692   $46.77   $46.75   $46.80  
  Purchase #5 $208.73   9.707%   $228.9914   $228.99   $229.00   $229.00  
  Purchase #6 $238.62   8.333%   $258.5042   $258.50   $258.50   $258.50  
  Purchase #7 $44.90   12.150%   $50.3554   $50.36   $50.35   $50.40  
  7 purchase totals = $993.43       $1,077.7264   $1,077.73   $1,077.70   $1,077.80