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 $108.57   9.561%   $118.9504   $118.95   $118.95   $119.00  
  Purchase #2 $68.73   10.596%   $76.0126   $76.01   $76.00   $76.00  
  Purchase #3 $80.56   11.341%   $89.6963   $89.70   $89.70   $89.70  
  Purchase #4 $32.55   10.635%   $36.0117   $36.01   $36.00   $36.00  
  Purchase #5 $5.57   7.604%   $5.9935   $5.99   $6.00   $6.00  
  Purchase #6 $172.65   13.132%   $195.3224   $195.32   $195.30   $195.30  
  Purchase #7 $168.96   8.524%   $183.3622   $183.36   $183.35   $183.40  
  7 purchase totals = $637.59       $705.3491   $705.34   $705.30   $705.40