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 $233.32   12.430%   $262.3217   $262.32   $262.30   $262.30  
  Purchase #2 $221.46   6.797%   $236.5126   $236.51   $236.50   $236.50  
  Purchase #3 $159.52   3.829%   $165.628   $165.63   $165.65   $165.60  
  Purchase #4 $151.39   6.293%   $160.917   $160.92   $160.90   $160.90  
  Purchase #5 $145.35   7.494%   $156.2425   $156.24   $156.25   $156.20  
  Purchase #6 $216.61   3.501%   $224.1935   $224.19   $224.20   $224.20  
  Purchase #7 $222.66   10.586%   $246.2308   $246.23   $246.25   $246.20  
  7 purchase totals = $1,350.31       $1,452.0461   $1,452.04   $1,452.05   $1,451.90