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 $95.94   11.646%   $107.1132   $107.11   $107.10   $107.10  
  Purchase #2 $178.82   11.311%   $199.0463   $199.05   $199.05   $199.00  
  Purchase #3 $148.26   12.701%   $167.0905   $167.09   $167.10   $167.10  
  Purchase #4 $205.67   5.168%   $216.299   $216.30   $216.30   $216.30  
  Purchase #5 $13.83   10.589%   $15.2945   $15.29   $15.30   $15.30  
  Purchase #6 $111.25   4.171%   $115.8902   $115.89   $115.90   $115.90  
  Purchase #7 $241.69   5.510%   $255.0071   $255.01   $255.00   $255.00  
  7 purchase totals = $995.46       $1,075.7408   $1,075.74   $1,075.75   $1,075.70