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 $233.77   3.298%   $241.4797   $241.48   $241.50   $241.50  
  Purchase #2 $162.89   12.503%   $183.2561   $183.26   $183.25   $183.30  
  Purchase #3 $232.98   12.332%   $261.7111   $261.71   $261.70   $261.70  
  Purchase #4 $87.29   13.363%   $98.9546   $98.95   $98.95   $99.00  
  Purchase #5 $202.96   11.339%   $225.9736   $225.97   $225.95   $226.00  
  Purchase #6 $237.67   12.149%   $266.5445   $266.54   $266.55   $266.50  
  Purchase #7 $167.93   9.566%   $183.9942   $183.99   $184.00   $184.00  
  7 purchase totals = $1,325.49       $1,461.9138   $1,461.90   $1,461.90   $1,462.00