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 $91.45   3.455%   $94.6096   $94.61   $94.60   $94.60  
  Purchase #2 $197.64   4.872%   $207.269   $207.27   $207.25   $207.30  
  Purchase #3 $95.91   11.737%   $107.167   $107.17   $107.15   $107.20  
  Purchase #4 $165.72   3.696%   $171.845   $171.85   $171.85   $171.80  
  Purchase #5 $84.30   12.237%   $94.6158   $94.62   $94.60   $94.60  
  Purchase #6 $208.83   3.866%   $216.9034   $216.90   $216.90   $216.90  
  Purchase #7 $30.87   11.166%   $34.3169   $34.32   $34.30   $34.30  
  7 purchase totals = $874.72       $926.7267   $926.74   $926.65   $926.70