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 $162.26   5.790%   $171.6549   $171.65   $171.65   $171.70  
  Purchase #2 $64.47   3.121%   $66.4821   $66.48   $66.50   $66.50  
  Purchase #3 $168.80   8.295%   $182.802   $182.80   $182.80   $182.80  
  Purchase #4 $208.99   7.597%   $224.867   $224.87   $224.85   $224.90  
  Purchase #5 $111.34   3.570%   $115.3148   $115.31   $115.30   $115.30  
  Purchase #6 $108.62   4.497%   $113.5046   $113.50   $113.50   $113.50  
  Purchase #7 $101.34   8.544%   $109.9985   $110.00   $110.00   $110.00  
  7 purchase totals = $925.82       $984.6239   $984.61   $984.60   $984.70