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 $232.42   8.110%   $251.2693   $251.27   $251.25   $251.30  
  Purchase #2 $224.70   7.709%   $242.0221   $242.02   $242.00   $242.00  
  Purchase #3 $50.68   13.755%   $57.651   $57.65   $57.65   $57.70  
  Purchase #4 $146.82   11.119%   $163.1449   $163.14   $163.15   $163.10  
  Purchase #5 $88.92   8.454%   $96.4373   $96.44   $96.45   $96.40  
  Purchase #6 $202.97   4.388%   $211.8763   $211.88   $211.90   $211.90  
  Purchase #7 $70.41   13.176%   $79.6872   $79.69   $79.70   $79.70  
  7 purchase totals = $1,016.92       $1,102.0881   $1,102.09   $1,102.10   $1,102.10