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 $181.50   10.734%   $200.9822   $200.98   $201.00   $201.00  
  Purchase #2 $87.80   7.444%   $94.3358   $94.34   $94.35   $94.30  
  Purchase #3 $46.98   10.667%   $51.9914   $51.99   $52.00   $52.00  
  Purchase #4 $112.48   4.307%   $117.3245   $117.32   $117.30   $117.30  
  Purchase #5 $79.42   4.222%   $82.7731   $82.77   $82.75   $82.80  
  Purchase #6 $180.81   6.329%   $192.2535   $192.25   $192.25   $192.30  
  Purchase #7 $200.55   7.852%   $216.2972   $216.30   $216.30   $216.30  
  7 purchase totals = $889.54       $955.9577   $955.95   $955.95   $956.00