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 $35.46   6.283%   $37.688   $37.69   $37.70   $37.70  
  Purchase #2 $174.78   6.814%   $186.6895   $186.69   $186.70   $186.70  
  Purchase #3 $10.96   11.310%   $12.1996   $12.20   $12.20   $12.20  
  Purchase #4 $146.52   5.450%   $154.5053   $154.51   $154.50   $154.50  
  Purchase #5 $58.35   6.462%   $62.1206   $62.12   $62.10   $62.10  
  Purchase #6 $239.80   5.717%   $253.5094   $253.51   $253.50   $253.50  
  Purchase #7 $232.39   11.167%   $258.341   $258.34   $258.35   $258.30  
  7 purchase totals = $898.26       $965.0534   $965.06   $965.05   $965.00