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 $83.96   12.788%   $94.6968   $94.70   $94.70   $94.70  
  Purchase #2 $218.40   10.371%   $241.0503   $241.05   $241.05   $241.10  
  Purchase #3 $167.95   10.822%   $186.1255   $186.13   $186.15   $186.10  
  Purchase #4 $14.96   12.346%   $16.807   $16.81   $16.80   $16.80  
  Purchase #5 $22.38   5.805%   $23.6792   $23.68   $23.70   $23.70  
  Purchase #6 $47.64   6.578%   $50.7738   $50.77   $50.75   $50.80  
  Purchase #7 $88.30   5.608%   $93.2519   $93.25   $93.25   $93.30  
  7 purchase totals = $643.59       $706.3845   $706.39   $706.40   $706.50