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 $205.94   5.258%   $216.7683   $216.77   $216.75   $216.80  
  Purchase #2 $159.51   9.771%   $175.0957   $175.10   $175.10   $175.10  
  Purchase #3 $44.48   3.242%   $45.922   $45.92   $45.90   $45.90  
  Purchase #4 $32.93   11.245%   $36.633   $36.63   $36.65   $36.60  
  Purchase #5 $131.51   13.478%   $149.2349   $149.23   $149.25   $149.20  
  Purchase #6 $198.74   12.582%   $223.7455   $223.75   $223.75   $223.70  
  Purchase #7 $240.60   7.653%   $259.0131   $259.01   $259.00   $259.00  
  7 purchase totals = $1,013.71       $1,106.4125   $1,106.41   $1,106.40   $1,106.30