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 $10.95   3.477%   $11.3307   $11.33   $11.35   $11.30  
  Purchase #2 $54.56   6.470%   $58.09   $58.09   $58.10   $58.10  
  Purchase #3 $53.26   10.328%   $58.7607   $58.76   $58.75   $58.80  
  Purchase #4 $245.59   11.707%   $274.3412   $274.34   $274.35   $274.30  
  Purchase #5 $96.96   3.804%   $100.6484   $100.65   $100.65   $100.60  
  Purchase #6 $207.70   6.350%   $220.889   $220.89   $220.90   $220.90  
  Purchase #7 $40.54   3.202%   $41.8381   $41.84   $41.85   $41.80  
  7 purchase totals = $709.56       $765.8981   $765.90   $765.95   $765.80