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 $88.91   5.808%   $94.0739   $94.07   $94.05   $94.10  
  Purchase #2 $202.61   7.571%   $217.9496   $217.95   $217.95   $217.90  
  Purchase #3 $186.57   3.215%   $192.5682   $192.57   $192.55   $192.60  
  Purchase #4 $223.45   12.526%   $251.4393   $251.44   $251.45   $251.40  
  Purchase #5 $100.62   8.342%   $109.0137   $109.01   $109.00   $109.00  
  Purchase #6 $40.28   10.184%   $44.3821   $44.38   $44.40   $44.40  
  Purchase #7 $232.58   11.599%   $259.557   $259.56   $259.55   $259.60  
  7 purchase totals = $1,075.02       $1,168.9838   $1,168.98   $1,168.95   $1,169.00