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 $32.78   4.759%   $34.34   $34.34   $34.35   $34.30  
  Purchase #2 $116.95   13.356%   $132.5698   $132.57   $132.55   $132.60  
  Purchase #3 $165.57   3.342%   $171.1033   $171.10   $171.10   $171.10  
  Purchase #4 $93.72   8.756%   $101.9261   $101.93   $101.95   $101.90  
  Purchase #5 $114.58   13.211%   $129.7172   $129.72   $129.70   $129.70  
  Purchase #6 $188.73   6.868%   $201.692   $201.69   $201.70   $201.70  
  Purchase #7 $219.70   12.798%   $247.8172   $247.82   $247.80   $247.80  
  7 purchase totals = $932.03       $1,019.1656   $1,019.17   $1,019.15   $1,019.10