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 $214.48   13.710%   $243.8852   $243.89   $243.90   $243.90  
  Purchase #2 $219.49   3.391%   $226.9329   $226.93   $226.95   $226.90  
  Purchase #3 $168.52   3.475%   $174.3761   $174.38   $174.40   $174.40  
  Purchase #4 $104.36   6.111%   $110.7374   $110.74   $110.75   $110.70  
  Purchase #5 $146.70   13.661%   $166.7407   $166.74   $166.75   $166.70  
  Purchase #6 $189.32   4.847%   $198.4963   $198.50   $198.50   $198.50  
  Purchase #7 $59.66   8.214%   $64.5605   $64.56   $64.55   $64.60  
  7 purchase totals = $1,102.53       $1,185.7291   $1,185.74   $1,185.80   $1,185.70