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 $226.66   6.744%   $241.946   $241.95   $241.95   $241.90  
  Purchase #2 $113.70   13.372%   $128.904   $128.90   $128.90   $128.90  
  Purchase #3 $53.41   10.613%   $59.0784   $59.08   $59.10   $59.10  
  Purchase #4 $178.57   13.839%   $203.2823   $203.28   $203.30   $203.30  
  Purchase #5 $58.25   10.862%   $64.5771   $64.58   $64.60   $64.60  
  Purchase #6 $224.66   6.461%   $239.1753   $239.18   $239.20   $239.20  
  Purchase #7 $190.27   10.713%   $210.6536   $210.65   $210.65   $210.70  
  7 purchase totals = $1,045.52       $1,147.6167   $1,147.62   $1,147.70   $1,147.70