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 $201.37   8.759%   $219.008   $219.01   $219.00   $219.00  
  Purchase #2 $209.45   5.210%   $220.3623   $220.36   $220.35   $220.40  
  Purchase #3 $66.75   8.696%   $72.5546   $72.55   $72.55   $72.60  
  Purchase #4 $221.93   7.762%   $239.1562   $239.16   $239.15   $239.20  
  Purchase #5 $181.89   12.158%   $204.0042   $204.00   $204.00   $204.00  
  Purchase #6 $136.59   12.120%   $153.1447   $153.14   $153.15   $153.10  
  Purchase #7 $150.81   3.110%   $155.5002   $155.50   $155.50   $155.50  
  7 purchase totals = $1,168.79       $1,263.7302   $1,263.72   $1,263.70   $1,263.80