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 $139.54   10.327%   $153.9503   $153.95   $153.95   $154.00  
  Purchase #2 $24.40   3.112%   $25.1593   $25.16   $25.15   $25.20  
  Purchase #3 $203.41   5.653%   $214.9088   $214.91   $214.90   $214.90  
  Purchase #4 $92.25   4.826%   $96.702   $96.70   $96.70   $96.70  
  Purchase #5 $214.59   6.830%   $229.2465   $229.25   $229.25   $229.20  
  Purchase #6 $177.66   7.651%   $191.2528   $191.25   $191.25   $191.30  
  Purchase #7 $181.88   11.531%   $202.8526   $202.85   $202.85   $202.90  
  7 purchase totals = $1,033.73       $1,114.0723   $1,114.07   $1,114.05   $1,114.20