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 $182.41   10.545%   $201.6451   $201.65   $201.65   $201.60  
  Purchase #2 $91.36   4.696%   $95.6503   $95.65   $95.65   $95.70  
  Purchase #3 $143.48   5.649%   $151.5852   $151.59   $151.60   $151.60  
  Purchase #4 $10.69   11.685%   $11.9391   $11.94   $11.95   $11.90  
  Purchase #5 $221.82   13.541%   $251.8566   $251.86   $251.85   $251.90  
  Purchase #6 $65.79   10.384%   $72.6216   $72.62   $72.60   $72.60  
  Purchase #7 $154.83   8.172%   $167.4827   $167.48   $167.50   $167.50  
  7 purchase totals = $870.38       $952.7806   $952.79   $952.80   $952.80