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 $69.48   4.689%   $72.7379   $72.74   $72.75   $72.70  
  Purchase #2 $216.62   3.175%   $223.4977   $223.50   $223.50   $223.50  
  Purchase #3 $232.50   5.436%   $245.1387   $245.14   $245.15   $245.10  
  Purchase #4 $54.87   8.509%   $59.5389   $59.54   $59.55   $59.50  
  Purchase #5 $167.37   9.564%   $183.3773   $183.38   $183.40   $183.40  
  Purchase #6 $49.57   11.417%   $55.2294   $55.23   $55.25   $55.20  
  Purchase #7 $22.72   5.590%   $23.99   $23.99   $24.00   $24.00  
  7 purchase totals = $813.13       $863.5099   $863.52   $863.60   $863.40