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 $184.93   5.259%   $194.6555   $194.66   $194.65   $194.70  
  Purchase #2 $66.58   6.675%   $71.0242   $71.02   $71.00   $71.00  
  Purchase #3 $216.83   12.818%   $244.6233   $244.62   $244.60   $244.60  
  Purchase #4 $23.31   11.335%   $25.9522   $25.95   $25.95   $26.00  
  Purchase #5 $99.38   6.749%   $106.0872   $106.09   $106.10   $106.10  
  Purchase #6 $219.34   6.293%   $233.1431   $233.14   $233.15   $233.10  
  Purchase #7 $242.76   5.295%   $255.6141   $255.61   $255.60   $255.60  
  7 purchase totals = $1,053.13       $1,131.0996   $1,131.09   $1,131.05   $1,131.10