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 $59.30   4.867%   $62.1861   $62.19   $62.20   $62.20  
  Purchase #2 $239.67   8.687%   $260.4901   $260.49   $260.50   $260.50  
  Purchase #3 $126.81   7.582%   $136.4247   $136.42   $136.40   $136.40  
  Purchase #4 $177.96   9.460%   $194.795   $194.80   $194.80   $194.80  
  Purchase #5 $81.66   11.579%   $91.1154   $91.12   $91.10   $91.10  
  Purchase #6 $218.25   9.156%   $238.233   $238.23   $238.25   $238.20  
  Purchase #7 $244.46   9.687%   $268.1408   $268.14   $268.15   $268.10  
  7 purchase totals = $1,148.11       $1,251.3851   $1,251.39   $1,251.40   $1,251.30