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 $61.34   11.299%   $68.2708   $68.27   $68.25   $68.30  
  Purchase #2 $167.94   4.163%   $174.9313   $174.93   $174.95   $174.90  
  Purchase #3 $247.73   7.335%   $265.901   $265.90   $265.90   $265.90  
  Purchase #4 $175.85   13.218%   $199.0939   $199.09   $199.10   $199.10  
  Purchase #5 $176.98   10.344%   $195.2868   $195.29   $195.30   $195.30  
  Purchase #6 $220.84   5.193%   $232.3082   $232.31   $232.30   $232.30  
  Purchase #7 $58.86   4.195%   $61.3292   $61.33   $61.35   $61.30  
  7 purchase totals = $1,109.54       $1,197.1212   $1,197.12   $1,197.15   $1,197.10