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 $175.95   11.205%   $195.6652   $195.67   $195.65   $195.70  
  Purchase #2 $30.94   5.824%   $32.7419   $32.74   $32.75   $32.70  
  Purchase #3 $33.43   3.246%   $34.5151   $34.52   $34.50   $34.50  
  Purchase #4 $204.71   5.253%   $215.4634   $215.46   $215.45   $215.50  
  Purchase #5 $133.41   5.115%   $140.2339   $140.23   $140.25   $140.20  
  Purchase #6 $245.34   4.578%   $256.5717   $256.57   $256.55   $256.60  
  Purchase #7 $235.51   5.766%   $249.0895   $249.09   $249.10   $249.10  
  7 purchase totals = $1,059.29       $1,124.2807   $1,124.28   $1,124.25   $1,124.30