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 $68.36   8.220%   $73.9792   $73.98   $74.00   $74.00  
  Purchase #2 $250.53   6.265%   $266.2257   $266.23   $266.25   $266.20  
  Purchase #3 $146.44   10.416%   $161.6932   $161.69   $161.70   $161.70  
  Purchase #4 $216.28   7.496%   $232.4923   $232.49   $232.50   $232.50  
  Purchase #5 $162.99   6.817%   $174.101   $174.10   $174.10   $174.10  
  Purchase #6 $50.37   4.245%   $52.5082   $52.51   $52.50   $52.50  
  Purchase #7 $142.97   8.649%   $155.3355   $155.34   $155.35   $155.30  
  7 purchase totals = $1,037.94       $1,116.3351   $1,116.34   $1,116.40   $1,116.30