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 $160.75   11.370%   $179.0273   $179.03   $179.05   $179.00  
  Purchase #2 $238.30   10.343%   $262.9474   $262.95   $262.95   $262.90  
  Purchase #3 $176.82   9.727%   $194.0193   $194.02   $194.00   $194.00  
  Purchase #4 $27.68   5.795%   $29.2841   $29.28   $29.30   $29.30  
  Purchase #5 $219.43   9.295%   $239.826   $239.83   $239.85   $239.80  
  Purchase #6 $22.97   4.426%   $23.9867   $23.99   $24.00   $24.00  
  Purchase #7 $243.47   9.661%   $266.9916   $266.99   $267.00   $267.00  
  7 purchase totals = $1,089.42       $1,196.0824   $1,196.09   $1,196.15   $1,196.00