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 $119.38   5.515%   $125.9638   $125.96   $125.95   $126.00  
  Purchase #2 $115.65   10.601%   $127.9101   $127.91   $127.90   $127.90  
  Purchase #3 $54.50   13.819%   $62.0314   $62.03   $62.05   $62.00  
  Purchase #4 $175.77   9.505%   $192.4769   $192.48   $192.50   $192.50  
  Purchase #5 $205.64   10.779%   $227.8059   $227.81   $227.80   $227.80  
  Purchase #6 $204.70   12.349%   $229.9784   $229.98   $230.00   $230.00  
  Purchase #7 $31.76   11.323%   $35.3562   $35.36   $35.35   $35.40  
  7 purchase totals = $907.40       $1,001.5227   $1,001.53   $1,001.55   $1,001.60