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 $214.40   5.186%   $225.5188   $225.52   $225.50   $225.50  
  Purchase #2 $64.68   6.654%   $68.9838   $68.98   $69.00   $69.00  
  Purchase #3 $201.92   13.145%   $228.4624   $228.46   $228.45   $228.50  
  Purchase #4 $140.75   4.388%   $146.9261   $146.93   $146.95   $146.90  
  Purchase #5 $9.84   8.387%   $10.6653   $10.67   $10.65   $10.70  
  Purchase #6 $232.93   3.808%   $241.8   $241.80   $241.80   $241.80  
  Purchase #7 $129.52   9.746%   $142.143   $142.14   $142.15   $142.10  
  7 purchase totals = $994.04       $1,064.4994   $1,064.50   $1,064.50   $1,064.50