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 $161.98   12.204%   $181.748   $181.75   $181.75   $181.70  
  Purchase #2 $201.78   4.665%   $211.193   $211.19   $211.20   $211.20  
  Purchase #3 $186.26   7.853%   $200.887   $200.89   $200.90   $200.90  
  Purchase #4 $58.76   5.516%   $62.0012   $62.00   $62.00   $62.00  
  Purchase #5 $44.87   4.802%   $47.0247   $47.02   $47.00   $47.00  
  Purchase #6 $43.38   6.237%   $46.0856   $46.09   $46.10   $46.10  
  Purchase #7 $192.75   10.801%   $213.5689   $213.57   $213.55   $213.60  
  7 purchase totals = $889.78       $962.5084   $962.51   $962.50   $962.50