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 $237.57   9.711%   $260.6404   $260.64   $260.65   $260.60  
  Purchase #2 $244.97   11.318%   $272.6957   $272.70   $272.70   $272.70  
  Purchase #3 $23.71   3.197%   $24.468   $24.47   $24.45   $24.50  
  Purchase #4 $122.82   6.616%   $130.9458   $130.95   $130.95   $130.90  
  Purchase #5 $37.69   12.817%   $42.5207   $42.52   $42.50   $42.50  
  Purchase #6 $222.37   6.712%   $237.2955   $237.30   $237.30   $237.30  
  Purchase #7 $124.32   10.658%   $137.57   $137.57   $137.55   $137.60  
  7 purchase totals = $1,013.45       $1,106.1361   $1,106.15   $1,106.10   $1,106.10