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 $195.98   5.759%   $207.2665   $207.27   $207.25   $207.30  
  Purchase #2 $92.98   3.419%   $96.159   $96.16   $96.15   $96.20  
  Purchase #3 $161.47   9.405%   $176.6563   $176.66   $176.65   $176.70  
  Purchase #4 $155.34   8.245%   $168.1478   $168.15   $168.15   $168.10  
  Purchase #5 $209.98   13.209%   $237.7163   $237.72   $237.70   $237.70  
  Purchase #6 $24.54   3.343%   $25.3604   $25.36   $25.35   $25.40  
  Purchase #7 $97.37   13.555%   $110.5685   $110.57   $110.55   $110.60  
  7 purchase totals = $937.66       $1,021.8748   $1,021.89   $1,021.80   $1,022.00