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 $59.49   5.457%   $62.7364   $62.74   $62.75   $62.70  
  Purchase #2 $230.52   3.779%   $239.2314   $239.23   $239.25   $239.20  
  Purchase #3 $22.58   9.477%   $24.7199   $24.72   $24.70   $24.70  
  Purchase #4 $220.45   9.748%   $241.9395   $241.94   $241.95   $241.90  
  Purchase #5 $129.96   12.535%   $146.2505   $146.25   $146.25   $146.30  
  Purchase #6 $60.67   7.288%   $65.0916   $65.09   $65.10   $65.10  
  Purchase #7 $213.74   10.281%   $235.7146   $235.71   $235.70   $235.70  
  7 purchase totals = $937.41       $1,015.6839   $1,015.68   $1,015.70   $1,015.60