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 $226.64   4.548%   $236.9476   $236.95   $236.95   $236.90  
  Purchase #2 $234.75   11.360%   $261.4176   $261.42   $261.40   $261.40  
  Purchase #3 $167.77   12.839%   $189.31   $189.31   $189.30   $189.30  
  Purchase #4 $221.93   5.480%   $234.0918   $234.09   $234.10   $234.10  
  Purchase #5 $61.39   7.410%   $65.939   $65.94   $65.95   $65.90  
  Purchase #6 $112.30   13.339%   $127.2797   $127.28   $127.30   $127.30  
  Purchase #7 $54.75   6.452%   $58.2825   $58.28   $58.30   $58.30  
  7 purchase totals = $1,079.53       $1,173.2682   $1,173.27   $1,173.30   $1,173.20