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 $209.38   13.643%   $237.9457   $237.95   $237.95   $237.90  
  Purchase #2 $47.66   11.304%   $53.0475   $53.05   $53.05   $53.00  
  Purchase #3 $47.39   9.241%   $51.7693   $51.77   $51.75   $51.80  
  Purchase #4 $167.92   5.375%   $176.9457   $176.95   $176.95   $176.90  
  Purchase #5 $246.85   4.159%   $257.1165   $257.12   $257.10   $257.10  
  Purchase #6 $179.82   11.153%   $199.8753   $199.88   $199.90   $199.90  
  Purchase #7 $82.59   12.864%   $93.2144   $93.21   $93.20   $93.20  
  7 purchase totals = $981.61       $1,069.9144   $1,069.93   $1,069.90   $1,069.80