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 $119.63   4.807%   $125.3806   $125.38   $125.40   $125.40  
  Purchase #2 $62.85   8.696%   $68.3154   $68.32   $68.30   $68.30  
  Purchase #3 $135.25   5.446%   $142.6157   $142.62   $142.60   $142.60  
  Purchase #4 $65.78   3.658%   $68.1862   $68.19   $68.20   $68.20  
  Purchase #5 $185.86   9.714%   $203.9144   $203.91   $203.90   $203.90  
  Purchase #6 $250.57   12.659%   $282.2897   $282.29   $282.30   $282.30  
  Purchase #7 $157.80   12.378%   $177.3325   $177.33   $177.35   $177.30  
  7 purchase totals = $977.74       $1,068.0345   $1,068.04   $1,068.05   $1,068.00