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 $215.94   8.564%   $234.4331   $234.43   $234.45   $234.40  
  Purchase #2 $178.35   11.116%   $198.1754   $198.18   $198.20   $198.20  
  Purchase #3 $43.36   12.281%   $48.685   $48.69   $48.70   $48.70  
  Purchase #4 $62.40   9.175%   $68.1252   $68.13   $68.15   $68.10  
  Purchase #5 $141.55   7.409%   $152.0374   $152.04   $152.05   $152.00  
  Purchase #6 $176.70   4.120%   $183.98   $183.98   $184.00   $184.00  
  Purchase #7 $17.59   9.836%   $19.3202   $19.32   $19.30   $19.30  
  7 purchase totals = $835.89       $904.7563   $904.77   $904.85   $904.70