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 $177.48   11.279%   $197.498   $197.50   $197.50   $197.50  
  Purchase #2 $113.98   8.455%   $123.617   $123.62   $123.60   $123.60  
  Purchase #3 $246.46   5.834%   $260.8385   $260.84   $260.85   $260.80  
  Purchase #4 $109.30   5.483%   $115.2929   $115.29   $115.30   $115.30  
  Purchase #5 $159.75   3.803%   $165.8253   $165.83   $165.85   $165.80  
  Purchase #6 $189.76   9.612%   $207.9997   $208.00   $208.00   $208.00  
  Purchase #7 $189.63   8.190%   $205.1607   $205.16   $205.15   $205.20  
  7 purchase totals = $1,186.36       $1,276.2321   $1,276.24   $1,276.25   $1,276.20