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 $191.85   11.621%   $214.1449   $214.14   $214.15   $214.10  
  Purchase #2 $212.27   5.771%   $224.5201   $224.52   $224.50   $224.50  
  Purchase #3 $34.84   12.161%   $39.0769   $39.08   $39.10   $39.10  
  Purchase #4 $49.98   8.549%   $54.2528   $54.25   $54.25   $54.30  
  Purchase #5 $165.68   6.737%   $176.8419   $176.84   $176.85   $176.80  
  Purchase #6 $240.95   6.225%   $255.9491   $255.95   $255.95   $255.90  
  Purchase #7 $153.89   5.705%   $162.6694   $162.67   $162.65   $162.70  
  7 purchase totals = $1,049.46       $1,127.4551   $1,127.45   $1,127.45   $1,127.40