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 $206.88   13.415%   $234.633   $234.63   $234.65   $234.60  
  Purchase #2 $242.92   13.768%   $276.3652   $276.37   $276.35   $276.40  
  Purchase #3 $15.60   4.651%   $16.3256   $16.33   $16.35   $16.30  
  Purchase #4 $227.41   11.313%   $253.1369   $253.14   $253.15   $253.10  
  Purchase #5 $60.79   13.392%   $68.931   $68.93   $68.95   $68.90  
  Purchase #6 $99.94   3.439%   $103.3769   $103.38   $103.40   $103.40  
  Purchase #7 $223.50   10.820%   $247.6827   $247.68   $247.70   $247.70  
  7 purchase totals = $1,077.04       $1,200.4513   $1,200.46   $1,200.55   $1,200.40