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 $192.52   11.177%   $214.038   $214.04   $214.05   $214.00  
  Purchase #2 $166.32   8.346%   $180.2011   $180.20   $180.20   $180.20  
  Purchase #3 $46.30   4.584%   $48.4224   $48.42   $48.40   $48.40  
  Purchase #4 $178.87   13.691%   $203.3591   $203.36   $203.35   $203.40  
  Purchase #5 $183.92   10.274%   $202.8159   $202.82   $202.80   $202.80  
  Purchase #6 $56.96   11.196%   $63.3372   $63.34   $63.35   $63.30  
  Purchase #7 $65.39   11.170%   $72.6941   $72.69   $72.70   $72.70  
  7 purchase totals = $890.28       $984.8678   $984.87   $984.85   $984.80