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 $184.61   5.130%   $194.0805   $194.08   $194.10   $194.10  
  Purchase #2 $102.86   8.432%   $111.5332   $111.53   $111.55   $111.50  
  Purchase #3 $123.99   11.110%   $137.7653   $137.77   $137.75   $137.80  
  Purchase #4 $66.42   11.589%   $74.1174   $74.12   $74.10   $74.10  
  Purchase #5 $178.74   8.281%   $193.5415   $193.54   $193.55   $193.50  
  Purchase #6 $60.95   3.801%   $63.2667   $63.27   $63.25   $63.30  
  Purchase #7 $220.86   5.379%   $232.7401   $232.74   $232.75   $232.70  
  7 purchase totals = $938.43       $1,007.0447   $1,007.05   $1,007.05   $1,007.00