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 $88.26   7.194%   $94.6094   $94.61   $94.60   $94.60  
  Purchase #2 $156.40   8.425%   $169.5767   $169.58   $169.60   $169.60  
  Purchase #3 $33.48   5.764%   $35.4098   $35.41   $35.40   $35.40  
  Purchase #4 $94.85   5.340%   $99.915   $99.92   $99.90   $99.90  
  Purchase #5 $35.32   4.359%   $36.8596   $36.86   $36.85   $36.90  
  Purchase #6 $172.33   11.449%   $192.0601   $192.06   $192.05   $192.10  
  Purchase #7 $141.68   11.236%   $157.5992   $157.60   $157.60   $157.60  
  7 purchase totals = $722.32       $786.0298   $786.04   $786.00   $786.10