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 $153.93   13.575%   $174.826   $174.83   $174.85   $174.80  
  Purchase #2 $232.75   12.641%   $262.1719   $262.17   $262.15   $262.20  
  Purchase #3 $61.29   12.206%   $68.7711   $68.77   $68.75   $68.80  
  Purchase #4 $229.35   11.597%   $255.9477   $255.95   $255.95   $255.90  
  Purchase #5 $178.60   9.408%   $195.4027   $195.40   $195.40   $195.40  
  Purchase #6 $115.43   7.359%   $123.9245   $123.92   $123.90   $123.90  
  Purchase #7 $142.43   9.506%   $155.9694   $155.97   $155.95   $156.00  
  7 purchase totals = $1,113.78       $1,237.0133   $1,237.01   $1,236.95   $1,237.00