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 $192.43   5.473%   $202.9617   $202.96   $202.95   $203.00  
  Purchase #2 $62.90   4.153%   $65.5122   $65.51   $65.50   $65.50  
  Purchase #3 $123.90   10.709%   $137.1685   $137.17   $137.15   $137.20  
  Purchase #4 $117.60   13.559%   $133.5454   $133.55   $133.55   $133.50  
  Purchase #5 $193.51   5.547%   $204.244   $204.24   $204.25   $204.20  
  Purchase #6 $61.70   5.412%   $65.0392   $65.04   $65.05   $65.00  
  Purchase #7 $203.25   5.527%   $214.4836   $214.48   $214.50   $214.50  
  7 purchase totals = $955.29       $1,022.9546   $1,022.95   $1,022.95   $1,022.90