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 $208.54   11.547%   $232.6201   $232.62   $232.60   $232.60  
  Purchase #2 $194.45   6.613%   $207.309   $207.31   $207.30   $207.30  
  Purchase #3 $111.92   5.160%   $117.6951   $117.70   $117.70   $117.70  
  Purchase #4 $106.94   11.180%   $118.8959   $118.90   $118.90   $118.90  
  Purchase #5 $74.99   6.309%   $79.7211   $79.72   $79.70   $79.70  
  Purchase #6 $106.83   4.150%   $111.2634   $111.26   $111.25   $111.30  
  Purchase #7 $201.41   12.598%   $226.7836   $226.78   $226.80   $226.80  
  7 purchase totals = $1,005.08       $1,094.2882   $1,094.29   $1,094.25   $1,094.30