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 $201.71   8.126%   $218.101   $218.10   $218.10   $218.10  
  Purchase #2 $51.33   5.829%   $54.322   $54.32   $54.30   $54.30  
  Purchase #3 $102.52   11.446%   $114.2544   $114.25   $114.25   $114.30  
  Purchase #4 $152.52   5.835%   $161.4195   $161.42   $161.40   $161.40  
  Purchase #5 $160.95   3.649%   $166.8231   $166.82   $166.80   $166.80  
  Purchase #6 $206.73   13.804%   $235.267   $235.27   $235.25   $235.30  
  Purchase #7 $135.41   6.792%   $144.607   $144.61   $144.60   $144.60  
  7 purchase totals = $1,011.17       $1,094.7940   $1,094.79   $1,094.70   $1,094.80