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 $62.76   5.113%   $65.9689   $65.97   $65.95   $66.00  
  Purchase #2 $129.93   13.547%   $147.5316   $147.53   $147.55   $147.50  
  Purchase #3 $238.88   9.152%   $260.7423   $260.74   $260.75   $260.70  
  Purchase #4 $164.41   13.669%   $186.8832   $186.88   $186.90   $186.90  
  Purchase #5 $93.95   13.515%   $106.6473   $106.65   $106.65   $106.60  
  Purchase #6 $150.54   11.839%   $168.3624   $168.36   $168.35   $168.40  
  Purchase #7 $206.79   13.712%   $235.145   $235.15   $235.15   $235.10  
  7 purchase totals = $1,047.26       $1,171.2807   $1,171.28   $1,171.30   $1,171.20