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 $61.68   11.232%   $68.6079   $68.61   $68.60   $68.60  
  Purchase #2 $246.96   6.644%   $263.368   $263.37   $263.35   $263.40  
  Purchase #3 $186.27   6.170%   $197.7629   $197.76   $197.75   $197.80  
  Purchase #4 $205.66   7.320%   $220.7143   $220.71   $220.70   $220.70  
  Purchase #5 $25.40   7.307%   $27.256   $27.26   $27.25   $27.30  
  Purchase #6 $222.95   3.793%   $231.4065   $231.41   $231.40   $231.40  
  Purchase #7 $22.75   6.122%   $24.1428   $24.14   $24.15   $24.10  
  7 purchase totals = $971.67       $1,033.2584   $1,033.26   $1,033.20   $1,033.30