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 $103.76   10.147%   $114.2885   $114.29   $114.30   $114.30  
  Purchase #2 $190.26   7.145%   $203.8541   $203.85   $203.85   $203.90  
  Purchase #3 $129.90   5.435%   $136.9601   $136.96   $136.95   $137.00  
  Purchase #4 $176.26   7.721%   $189.869   $189.87   $189.85   $189.90  
  Purchase #5 $220.67   5.783%   $233.4313   $233.43   $233.45   $233.40  
  Purchase #6 $39.82   6.652%   $42.4688   $42.47   $42.45   $42.50  
  Purchase #7 $167.88   10.107%   $184.8476   $184.85   $184.85   $184.80  
  7 purchase totals = $1,028.55       $1,105.7194   $1,105.72   $1,105.70   $1,105.80