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 $93.86   5.689%   $99.1997   $99.20   $99.20   $99.20  
  Purchase #2 $148.62   4.462%   $155.2514   $155.25   $155.25   $155.30  
  Purchase #3 $163.59   7.329%   $175.5795   $175.58   $175.60   $175.60  
  Purchase #4 $114.90   12.791%   $129.5969   $129.60   $129.60   $129.60  
  Purchase #5 $211.55   9.525%   $231.7001   $231.70   $231.70   $231.70  
  Purchase #6 $151.70   9.265%   $165.755   $165.76   $165.75   $165.80  
  Purchase #7 $174.32   11.595%   $194.5324   $194.53   $194.55   $194.50  
  7 purchase totals = $1,058.54       $1,151.6150   $1,151.62   $1,151.65   $1,151.70