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 $64.98   13.864%   $73.9888   $73.99   $74.00   $74.00  
  Purchase #2 $228.90   5.463%   $241.4048   $241.40   $241.40   $241.40  
  Purchase #3 $157.59   12.725%   $177.6433   $177.64   $177.65   $177.60  
  Purchase #4 $233.95   6.391%   $248.9017   $248.90   $248.90   $248.90  
  Purchase #5 $238.84   3.142%   $246.3444   $246.34   $246.35   $246.30  
  Purchase #6 $128.74   10.388%   $142.1135   $142.11   $142.10   $142.10  
  Purchase #7 $249.42   4.868%   $261.5618   $261.56   $261.55   $261.60  
  7 purchase totals = $1,302.42       $1,391.9583   $1,391.94   $1,391.95   $1,391.90