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 $186.60   8.120%   $201.7519   $201.75   $201.75   $201.80  
  Purchase #2 $139.57   7.738%   $150.3699   $150.37   $150.35   $150.40  
  Purchase #3 $59.83   12.703%   $67.4302   $67.43   $67.45   $67.40  
  Purchase #4 $46.38   4.743%   $48.5798   $48.58   $48.60   $48.60  
  Purchase #5 $152.32   6.769%   $162.6305   $162.63   $162.65   $162.60  
  Purchase #6 $247.27   6.872%   $264.2624   $264.26   $264.25   $264.30  
  Purchase #7 $233.65   3.223%   $241.1805   $241.18   $241.20   $241.20  
  7 purchase totals = $1,065.62       $1,136.2052   $1,136.20   $1,136.25   $1,136.30