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 $205.61   6.610%   $219.2008   $219.20   $219.20   $219.20  
  Purchase #2 $41.78   13.212%   $47.3   $47.30   $47.30   $47.30  
  Purchase #3 $73.77   11.353%   $82.1451   $82.15   $82.15   $82.10  
  Purchase #4 $45.28   4.606%   $47.3656   $47.37   $47.35   $47.40  
  Purchase #5 $190.73   12.852%   $215.2426   $215.24   $215.25   $215.20  
  Purchase #6 $198.78   10.525%   $219.7016   $219.70   $219.70   $219.70  
  Purchase #7 $221.44   5.146%   $232.8353   $232.84   $232.85   $232.80  
  7 purchase totals = $977.39       $1,063.7910   $1,063.80   $1,063.80   $1,063.70