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 $95.41   12.835%   $107.6559   $107.66   $107.65   $107.70  
  Purchase #2 $100.26   6.136%   $106.412   $106.41   $106.40   $106.40  
  Purchase #3 $119.51   11.840%   $133.66   $133.66   $133.65   $133.70  
  Purchase #4 $93.69   10.625%   $103.6446   $103.64   $103.65   $103.60  
  Purchase #5 $54.39   5.279%   $57.2612   $57.26   $57.25   $57.30  
  Purchase #6 $67.85   7.337%   $72.8282   $72.83   $72.85   $72.80  
  Purchase #7 $161.64   12.274%   $181.4797   $181.48   $181.50   $181.50  
  7 purchase totals = $692.75       $762.9416   $762.94   $762.95   $763.00