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 $174.66   12.738%   $196.9082   $196.91   $196.90   $196.90  
  Purchase #2 $168.77   4.384%   $176.1689   $176.17   $176.15   $176.20  
  Purchase #3 $67.67   9.220%   $73.9092   $73.91   $73.90   $73.90  
  Purchase #4 $166.45   10.239%   $183.4928   $183.49   $183.50   $183.50  
  Purchase #5 $46.40   5.554%   $48.9771   $48.98   $49.00   $49.00  
  Purchase #6 $235.89   10.170%   $259.88   $259.88   $259.90   $259.90  
  Purchase #7 $153.51   11.339%   $170.9165   $170.92   $170.90   $170.90  
  7 purchase totals = $1,013.35       $1,110.2527   $1,110.26   $1,110.25   $1,110.30