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 $178.77   9.236%   $195.2812   $195.28   $195.30   $195.30  
  Purchase #2 $247.51   11.188%   $275.2014   $275.20   $275.20   $275.20  
  Purchase #3 $54.30   10.450%   $59.9744   $59.97   $59.95   $60.00  
  Purchase #4 $40.38   7.798%   $43.5288   $43.53   $43.55   $43.50  
  Purchase #5 $204.58   6.125%   $217.1105   $217.11   $217.10   $217.10  
  Purchase #6 $183.91   6.709%   $196.2485   $196.25   $196.25   $196.20  
  Purchase #7 $248.55   10.128%   $273.7231   $273.72   $273.70   $273.70  
  7 purchase totals = $1,158.00       $1,261.0679   $1,261.06   $1,261.05   $1,261.00