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 $182.81   10.494%   $201.9941   $201.99   $202.00   $202.00  
  Purchase #2 $56.91   8.767%   $61.8993   $61.90   $61.90   $61.90  
  Purchase #3 $185.32   3.178%   $191.2095   $191.21   $191.20   $191.20  
  Purchase #4 $92.61   3.656%   $95.9958   $96.00   $96.00   $96.00  
  Purchase #5 $192.67   9.786%   $211.5247   $211.52   $211.50   $211.50  
  Purchase #6 $105.93   10.294%   $116.8344   $116.83   $116.85   $116.80  
  Purchase #7 $250.79   6.510%   $267.1164   $267.12   $267.10   $267.10  
  7 purchase totals = $1,067.04       $1,146.5742   $1,146.57   $1,146.55   $1,146.50