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 $41.97   5.512%   $44.2834   $44.28   $44.30   $44.30  
  Purchase #2 $140.38   8.135%   $151.7999   $151.80   $151.80   $151.80  
  Purchase #3 $52.53   9.450%   $57.4941   $57.49   $57.50   $57.50  
  Purchase #4 $44.86   3.797%   $46.5633   $46.56   $46.55   $46.60  
  Purchase #5 $223.88   6.709%   $238.9001   $238.90   $238.90   $238.90  
  Purchase #6 $149.34   11.304%   $166.2214   $166.22   $166.20   $166.20  
  Purchase #7 $38.82   5.609%   $40.9974   $41.00   $41.00   $41.00  
  7 purchase totals = $691.78       $746.2596   $746.25   $746.25   $746.30