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 $110.32   13.606%   $125.3301   $125.33   $125.35   $125.30  
  Purchase #2 $58.93   9.571%   $64.5702   $64.57   $64.55   $64.60  
  Purchase #3 $231.33   12.329%   $259.8507   $259.85   $259.85   $259.90  
  Purchase #4 $101.66   4.534%   $106.2693   $106.27   $106.25   $106.30  
  Purchase #5 $177.59   9.662%   $194.7487   $194.75   $194.75   $194.70  
  Purchase #6 $227.25   8.417%   $246.3776   $246.38   $246.40   $246.40  
  Purchase #7 $69.70   11.661%   $77.8277   $77.83   $77.85   $77.80  
  7 purchase totals = $976.78       $1,074.9743   $1,074.98   $1,075.00   $1,075.00