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 $58.81   6.255%   $62.4886   $62.49   $62.50   $62.50  
  Purchase #2 $23.53   10.400%   $25.9771   $25.98   $26.00   $26.00  
  Purchase #3 $172.90   9.713%   $189.6938   $189.69   $189.70   $189.70  
  Purchase #4 $132.92   4.749%   $139.2324   $139.23   $139.25   $139.20  
  Purchase #5 $241.72   4.699%   $253.0784   $253.08   $253.10   $253.10  
  Purchase #6 $83.43   4.165%   $86.9049   $86.90   $86.90   $86.90  
  Purchase #7 $69.94   7.701%   $75.3261   $75.33   $75.35   $75.30  
  7 purchase totals = $783.25       $832.7013   $832.70   $832.80   $832.70