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 $85.99   8.102%   $92.9569   $92.96   $92.95   $93.00  
  Purchase #2 $52.97   3.563%   $54.8573   $54.86   $54.85   $54.90  
  Purchase #3 $215.55   7.808%   $232.3801   $232.38   $232.40   $232.40  
  Purchase #4 $191.58   4.756%   $200.6915   $200.69   $200.70   $200.70  
  Purchase #5 $159.74   3.464%   $165.2734   $165.27   $165.25   $165.30  
  Purchase #6 $193.67   7.273%   $207.7556   $207.76   $207.75   $207.80  
  Purchase #7 $194.37   6.694%   $207.3811   $207.38   $207.40   $207.40  
  7 purchase totals = $1,093.87       $1,161.2959   $1,161.30   $1,161.30   $1,161.50