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 $108.66   5.799%   $114.9612   $114.96   $114.95   $115.00  
  Purchase #2 $181.37   10.758%   $200.8818   $200.88   $200.90   $200.90  
  Purchase #3 $53.44   7.318%   $57.3507   $57.35   $57.35   $57.40  
  Purchase #4 $223.64   9.409%   $244.6823   $244.68   $244.70   $244.70  
  Purchase #5 $193.99   11.531%   $216.359   $216.36   $216.35   $216.40  
  Purchase #6 $162.27   4.318%   $169.2768   $169.28   $169.30   $169.30  
  Purchase #7 $74.38   10.112%   $81.9013   $81.90   $81.90   $81.90  
  7 purchase totals = $997.75       $1,085.4131   $1,085.41   $1,085.45   $1,085.60