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 $184.81   13.488%   $209.7372   $209.74   $209.75   $209.70  
  Purchase #2 $111.80   5.302%   $117.7276   $117.73   $117.75   $117.70  
  Purchase #3 $165.57   4.206%   $172.5339   $172.53   $172.55   $172.50  
  Purchase #4 $193.31   7.549%   $207.903   $207.90   $207.90   $207.90  
  Purchase #5 $222.41   4.340%   $232.0626   $232.06   $232.05   $232.10  
  Purchase #6 $197.78   9.274%   $216.1221   $216.12   $216.10   $216.10  
  Purchase #7 $48.99   6.127%   $51.9916   $51.99   $52.00   $52.00  
  7 purchase totals = $1,124.67       $1,208.0780   $1,208.07   $1,208.10   $1,208.00