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 $176.48   8.554%   $191.5761   $191.58   $191.60   $191.60  
  Purchase #2 $43.79   5.865%   $46.3583   $46.36   $46.35   $46.40  
  Purchase #3 $27.39   9.846%   $30.0868   $30.09   $30.10   $30.10  
  Purchase #4 $237.62   13.210%   $269.0096   $269.01   $269.00   $269.00  
  Purchase #5 $5.86   7.249%   $6.2848   $6.28   $6.30   $6.30  
  Purchase #6 $203.70   5.392%   $214.6835   $214.68   $214.70   $214.70  
  Purchase #7 $178.74   10.169%   $196.9161   $196.92   $196.90   $196.90  
  7 purchase totals = $873.58       $954.9152   $954.92   $954.95   $955.00