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 $100.30   13.795%   $114.1364   $114.14   $114.15   $114.10  
  Purchase #2 $184.68   6.594%   $196.8578   $196.86   $196.85   $196.90  
  Purchase #3 $237.44   12.733%   $267.6732   $267.67   $267.65   $267.70  
  Purchase #4 $210.67   9.764%   $231.2398   $231.24   $231.25   $231.20  
  Purchase #5 $114.65   9.809%   $125.896   $125.90   $125.90   $125.90  
  Purchase #6 $218.95   6.111%   $232.33   $232.33   $232.35   $232.30  
  Purchase #7 $7.45   3.607%   $7.7187   $7.72   $7.70   $7.70  
  7 purchase totals = $1,074.14       $1,175.8519   $1,175.86   $1,175.85   $1,175.80