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 $183.41   6.469%   $195.2748   $195.27   $195.25   $195.30  
  Purchase #2 $17.53   7.107%   $18.7759   $18.78   $18.80   $18.80  
  Purchase #3 $20.88   7.471%   $22.4399   $22.44   $22.45   $22.40  
  Purchase #4 $76.32   4.267%   $79.5766   $79.58   $79.60   $79.60  
  Purchase #5 $143.51   11.700%   $160.3007   $160.30   $160.30   $160.30  
  Purchase #6 $182.60   10.615%   $201.983   $201.98   $202.00   $202.00  
  Purchase #7 $78.84   8.204%   $85.308   $85.31   $85.30   $85.30  
  7 purchase totals = $703.09       $763.6589   $763.66   $763.70   $763.70