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 $163.81   11.259%   $182.2534   $182.25   $182.25   $182.30  
  Purchase #2 $88.82   10.700%   $98.3237   $98.32   $98.30   $98.30  
  Purchase #3 $194.36   4.304%   $202.7253   $202.73   $202.75   $202.70  
  Purchase #4 $164.71   3.708%   $170.8174   $170.82   $170.80   $170.80  
  Purchase #5 $69.48   4.781%   $72.8018   $72.80   $72.80   $72.80  
  Purchase #6 $161.34   12.332%   $181.2364   $181.24   $181.25   $181.20  
  Purchase #7 $107.45   5.268%   $113.1105   $113.11   $113.10   $113.10  
  7 purchase totals = $949.97       $1,021.2685   $1,021.27   $1,021.25   $1,021.20