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 $188.29   7.402%   $202.2272   $202.23   $202.25   $202.20  
  Purchase #2 $96.58   11.345%   $107.537   $107.54   $107.55   $107.50  
  Purchase #3 $103.79   13.527%   $117.8297   $117.83   $117.85   $117.80  
  Purchase #4 $52.34   7.845%   $56.4461   $56.45   $56.45   $56.40  
  Purchase #5 $173.94   7.194%   $186.4532   $186.45   $186.45   $186.50  
  Purchase #6 $93.43   13.519%   $106.0608   $106.06   $106.05   $106.10  
  Purchase #7 $165.58   8.853%   $180.2388   $180.24   $180.25   $180.20  
  7 purchase totals = $873.95       $956.7928   $956.80   $956.85   $956.70