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 $43.94   5.498%   $46.3558   $46.36   $46.35   $46.40  
  Purchase #2 $161.39   4.143%   $168.0764   $168.08   $168.10   $168.10  
  Purchase #3 $55.99   11.438%   $62.3941   $62.39   $62.40   $62.40  
  Purchase #4 $89.57   5.493%   $94.4901   $94.49   $94.50   $94.50  
  Purchase #5 $115.46   4.638%   $120.815   $120.82   $120.80   $120.80  
  Purchase #6 $181.82   6.683%   $193.971   $193.97   $193.95   $194.00  
  Purchase #7 $220.29   10.545%   $243.5196   $243.52   $243.50   $243.50  
  7 purchase totals = $868.46       $929.6220   $929.63   $929.60   $929.70