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 $87.80   7.291%   $94.2015   $94.20   $94.20   $94.20  
  Purchase #2 $220.29   8.136%   $238.2128   $238.21   $238.20   $238.20  
  Purchase #3 $153.99   7.107%   $164.9341   $164.93   $164.95   $164.90  
  Purchase #4 $226.25   7.399%   $242.9902   $242.99   $243.00   $243.00  
  Purchase #5 $249.49   5.538%   $263.3068   $263.31   $263.30   $263.30  
  Purchase #6 $236.41   9.324%   $258.4529   $258.45   $258.45   $258.50  
  Purchase #7 $192.90   7.147%   $206.6866   $206.69   $206.70   $206.70  
  7 purchase totals = $1,367.13       $1,468.7849   $1,468.78   $1,468.80   $1,468.80