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 $116.86   4.546%   $122.1725   $122.17   $122.15   $122.20  
  Purchase #2 $249.25   13.102%   $281.9067   $281.91   $281.90   $281.90  
  Purchase #3 $180.65   12.834%   $203.8346   $203.83   $203.85   $203.80  
  Purchase #4 $134.37   3.187%   $138.6524   $138.65   $138.65   $138.70  
  Purchase #5 $44.47   6.778%   $47.4842   $47.48   $47.50   $47.50  
  Purchase #6 $229.82   3.490%   $237.8407   $237.84   $237.85   $237.80  
  Purchase #7 $65.77   5.407%   $69.3262   $69.33   $69.35   $69.30  
  7 purchase totals = $1,021.19       $1,101.2173   $1,101.21   $1,101.25   $1,101.20