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 $182.94   11.293%   $203.5994   $203.60   $203.60   $203.60  
  Purchase #2 $246.66   6.450%   $262.5696   $262.57   $262.55   $262.60  
  Purchase #3 $220.55   5.826%   $233.3992   $233.40   $233.40   $233.40  
  Purchase #4 $73.95   8.515%   $80.2468   $80.25   $80.25   $80.20  
  Purchase #5 $69.51   9.594%   $76.1788   $76.18   $76.20   $76.20  
  Purchase #6 $174.77   7.283%   $187.4985   $187.50   $187.50   $187.50  
  Purchase #7 $49.43   4.374%   $51.5921   $51.59   $51.60   $51.60  
  7 purchase totals = $1,017.81       $1,095.0844   $1,095.09   $1,095.10   $1,095.10