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 $175.64   10.227%   $193.6027   $193.60   $193.60   $193.60  
  Purchase #2 $205.33   3.328%   $212.1634   $212.16   $212.15   $212.20  
  Purchase #3 $120.54   10.823%   $133.586   $133.59   $133.60   $133.60  
  Purchase #4 $130.31   6.435%   $138.6954   $138.70   $138.70   $138.70  
  Purchase #5 $163.80   13.294%   $185.5756   $185.58   $185.60   $185.60  
  Purchase #6 $151.94   4.412%   $158.6436   $158.64   $158.65   $158.60  
  Purchase #7 $188.58   7.136%   $202.0371   $202.04   $202.05   $202.00  
  7 purchase totals = $1,136.14       $1,224.3038   $1,224.31   $1,224.35   $1,224.30