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 $111.65   13.620%   $126.8567   $126.86   $126.85   $126.90  
  Purchase #2 $210.93   11.413%   $235.0034   $235.00   $235.00   $235.00  
  Purchase #3 $57.49   8.213%   $62.2117   $62.21   $62.20   $62.20  
  Purchase #4 $195.36   9.725%   $214.3588   $214.36   $214.35   $214.40  
  Purchase #5 $175.64   6.344%   $186.7826   $186.78   $186.80   $186.80  
  Purchase #6 $168.47   13.327%   $190.922   $190.92   $190.90   $190.90  
  Purchase #7 $9.29   13.771%   $10.5693   $10.57   $10.55   $10.60  
  7 purchase totals = $928.83       $1,026.7045   $1,026.70   $1,026.65   $1,026.80