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 $76.50   11.761%   $85.4972   $85.50   $85.50   $85.50  
  Purchase #2 $194.40   12.259%   $218.2315   $218.23   $218.25   $218.20  
  Purchase #3 $150.72   9.275%   $164.6993   $164.70   $164.70   $164.70  
  Purchase #4 $154.70   9.311%   $169.1041   $169.10   $169.10   $169.10  
  Purchase #5 $240.28   4.824%   $251.8711   $251.87   $251.85   $251.90  
  Purchase #6 $144.47   10.127%   $159.1005   $159.10   $159.10   $159.10  
  Purchase #7 $198.68   4.488%   $207.5968   $207.60   $207.60   $207.60  
  7 purchase totals = $1,159.75       $1,256.1005   $1,256.10   $1,256.10   $1,256.10