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 $111.92   12.788%   $126.2323   $126.23   $126.25   $126.20  
  Purchase #2 $241.33   5.401%   $254.3642   $254.36   $254.35   $254.40  
  Purchase #3 $228.74   4.800%   $239.7195   $239.72   $239.70   $239.70  
  Purchase #4 $156.50   10.326%   $172.6602   $172.66   $172.65   $172.70  
  Purchase #5 $44.37   5.318%   $46.7296   $46.73   $46.75   $46.70  
  Purchase #6 $137.79   6.559%   $146.8276   $146.83   $146.85   $146.80  
  Purchase #7 $36.61   9.292%   $40.0118   $40.01   $40.00   $40.00  
  7 purchase totals = $957.26       $1,026.5452   $1,026.54   $1,026.55   $1,026.50