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 $213.71   9.810%   $234.675   $234.68   $234.70   $234.70  
  Purchase #2 $156.90   12.622%   $176.7039   $176.70   $176.70   $176.70  
  Purchase #3 $41.39   12.598%   $46.6043   $46.60   $46.60   $46.60  
  Purchase #4 $233.74   4.787%   $244.9291   $244.93   $244.95   $244.90  
  Purchase #5 $131.58   9.525%   $144.113   $144.11   $144.10   $144.10  
  Purchase #6 $233.83   12.211%   $262.383   $262.38   $262.40   $262.40  
  Purchase #7 $32.89   8.359%   $35.6393   $35.64   $35.65   $35.60  
  7 purchase totals = $1,044.04       $1,145.0476   $1,145.04   $1,145.10   $1,145.00