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 $70.90   3.831%   $73.6162   $73.62   $73.60   $73.60  
  Purchase #2 $86.45   13.318%   $97.9634   $97.96   $97.95   $98.00  
  Purchase #3 $224.29   10.856%   $248.6389   $248.64   $248.65   $248.60  
  Purchase #4 $63.96   9.227%   $69.8616   $69.86   $69.85   $69.90  
  Purchase #5 $239.47   7.689%   $257.8828   $257.88   $257.90   $257.90  
  Purchase #6 $134.96   7.622%   $145.2467   $145.25   $145.25   $145.20  
  Purchase #7 $140.71   13.316%   $159.4469   $159.45   $159.45   $159.40  
  7 purchase totals = $960.74       $1,052.6565   $1,052.66   $1,052.65   $1,052.60