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 $62.97   10.639%   $69.6694   $69.67   $69.65   $69.70  
  Purchase #2 $201.72   3.388%   $208.5543   $208.55   $208.55   $208.60  
  Purchase #3 $169.98   5.375%   $179.1164   $179.12   $179.10   $179.10  
  Purchase #4 $198.94   7.629%   $214.1171   $214.12   $214.10   $214.10  
  Purchase #5 $199.55   8.363%   $216.2384   $216.24   $216.25   $216.20  
  Purchase #6 $117.59   13.789%   $133.8045   $133.80   $133.80   $133.80  
  Purchase #7 $244.34   11.159%   $271.6059   $271.61   $271.60   $271.60  
  7 purchase totals = $1,195.09       $1,293.1060   $1,293.11   $1,293.05   $1,293.10