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 $47.51   9.690%   $52.1137   $52.11   $52.10   $52.10  
  Purchase #2 $186.38   10.861%   $206.6227   $206.62   $206.60   $206.60  
  Purchase #3 $216.99   8.150%   $234.6747   $234.67   $234.65   $234.70  
  Purchase #4 $148.53   11.709%   $165.9214   $165.92   $165.90   $165.90  
  Purchase #5 $208.92   6.133%   $221.7331   $221.73   $221.75   $221.70  
  Purchase #6 $193.58   9.302%   $211.5868   $211.59   $211.60   $211.60  
  Purchase #7 $50.64   9.423%   $55.4118   $55.41   $55.40   $55.40  
  7 purchase totals = $1,052.55       $1,148.0642   $1,148.05   $1,148.00   $1,148.00