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 $204.86   5.695%   $216.5268   $216.53   $216.55   $216.50  
  Purchase #2 $180.91   6.479%   $192.6312   $192.63   $192.65   $192.60  
  Purchase #3 $104.74   10.736%   $115.9849   $115.98   $116.00   $116.00  
  Purchase #4 $20.60   11.859%   $23.043   $23.04   $23.05   $23.00  
  Purchase #5 $86.94   4.269%   $90.6515   $90.65   $90.65   $90.70  
  Purchase #6 $119.62   11.216%   $133.0366   $133.04   $133.05   $133.00  
  Purchase #7 $240.63   9.151%   $262.6501   $262.65   $262.65   $262.70  
  7 purchase totals = $958.30       $1,034.5241   $1,034.52   $1,034.60   $1,034.50