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 $57.94   8.238%   $62.7131   $62.71   $62.70   $62.70  
  Purchase #2 $196.61   8.596%   $213.5106   $213.51   $213.50   $213.50  
  Purchase #3 $9.73   3.833%   $10.103   $10.10   $10.10   $10.10  
  Purchase #4 $199.93   4.561%   $209.0488   $209.05   $209.05   $209.00  
  Purchase #5 $112.89   5.399%   $118.9849   $118.98   $119.00   $119.00  
  Purchase #6 $106.74   3.104%   $110.0532   $110.05   $110.05   $110.10  
  Purchase #7 $38.88   13.835%   $44.259   $44.26   $44.25   $44.30  
  7 purchase totals = $722.72       $768.6726   $768.66   $768.65   $768.70